From a certain point of view? I suppose. But in the grander scheme of things the gist of the Au Ra isn't too unique. Like.. The models to the girl Au Ra are incredibly similar to the Miqo'te. The men are fairly similar to Elezen, but I notice a whole lot more differences due to the shapely hips, shoulder width, height, outrageous hair options, large scale patches, and the way the chin crests help add mass and shape to the chins and face that I feel they're at least more unique, those things are notably lacking on girl Au Ra. Plus I feel that saying sexual dimorphism is the unique part of the Auri racial identity is downplaying the sexual dimorphism exhibited with the Roegadyn, another race with massive differences between men and women, the only difference is the heights are more closer together, but I feel that's heights kinda negligible by the fact that Roegadyn women bodies are literally half the thickness and width that the guys are. I just feel the Roegadyn at least shake it up a bit with the addition of a unique body shape for the women as well as the fact that the Roegadyn men are so massive, that even with the extreme levels of sexual dimorphism, the girls are still as large as any other race, so you'll see little complaints from me directed towards there.
I still do agree with you in that it's plausible, though I feel sex-linked should be more aptly described testosterone-linked, but I feel that even when given the option to make the women larger through things outside of just sex-linked genetics SE decided to not do it. It's not that the women of the Olkund were still comparatively short to the men of the Olkund, they were just average height in general, I find it completely bizarre that SE makes it so that the women of a humanoid race are so concrete in their height that even through selective breeding they couldn't even get any larger. After all there is more than just sex-linked genetics behind the height of any species. On a side note, I find it weird that the max Auri men can go to are 7'3, while the Olkund would be over 7'5 inches, I wonder why SE didn't make the height slider go higher with regards to that tribe.
It's more the motif of the warrior (Which the Xaela tribes generally give off) and all that the motif entails (Large size, more animal like features, aggressive appearance), like I understand that anyone can be a warrior and have immense success in battle, but it's such a tiring trope whenever the guys have a clear connection to the motif of "warrior" that's lacking on the women of that race entirely. Sure they're mentions of the men being househusbands and the amazon warrior tribe, but do you honestly look at them and get that feeling from their appearance? I know there's the whole "Actions speak louder than words (Or visuals in this scenario)" would say "My Lalafell DRK can wreck dragons and everything with a bad of their wrists! Your points are moot!" But to that I say, when you think "Warrior race" do you think the Miqo'te or the Amalj'aa fit better with that direction in terms of design? As a slightly related example, consider the Disney movie Mulan! The main enemies of the Chinese and Mulan were massive, but funnily enough, they were also the mongols, historically short (And stout) people. Why did Disney change this? Because they know the audience would look at the struggles of Mulan and the Chinese forces as much less severe if the enemy didn't fit the motif of pillaging destroying warrior. Likewise, it's neither unnatural nor unreasonable for one to come to the conclusion that things like the Dazkar or Borlaaq were more so added on haphazardly because they don't fit with the motif of the Au Ra. Why would there be a tribe full of warrior women when Auri women were designed to look as nadeshiko as possible? You could come to the conclusion and say "Well SE wanted to deviate a little from the trope which is good!", but it feels more like they were trying to cover their rears whenever they realized that the look of Auri women doesn't fit in with the motif of the Xaela so they have to make "exceptions" to prove that they weren't just making the race to pander to a certain demographic and keep discussions like these from occurring. It's just a tiredness of the tired reused trope of " Race with Small(er), cute(r) women and big(ger), scary(ier) men". If SE wanted to make sexual dimorphism the motif of the race, it could've been implemented in more unique ways, my personal favorite is the reverse of the stereotypical and making the men waifish while the women are strong and threatening.
Why field any men if they can just be outmatched with women archers? It's because SE (And anyone doing fantasy to be honest and fair) is more concerned with motifs than they are with perfect sense, which is fine, it's a fantasy game where shields (magic or otherwise) protect swordsmen til they get up close and cleave whatever archer in half because archers never carry melee weapons in fantasy. They've even implemented this whole idea of being liberal with regards to fantasy into the lore of the Au Ra with the Olkund purposely trying to make their tribe's members' as large as possible, but SE decided to take the lazy route of going with a "But for whatever reason (Be it genetics or just the unwillingness to make the Auri women tall) women remain at average height". Could they have made their a few exceptions to the whole "Small cute girls, big mean-looking men"? Absolutely, and I'd argue it'd be the best to allow this, because ultimately that's the only way SE could've killed any of this by allowing a few exceptions and allow players to fill in the gaps lore wise. As an example, make it so that the Auri women are generally small, but make it so that the height slider goes up to 7', that way the player can go "Oh well, my Au Ra comes from a tribe where they spent centuries making the women as tough as men through magic herbs and whatnot!", which isn't unheard of as the lore for the Xaela has the whole Tribes forgotten/hidden away allowing for that freedom to occur. Of course the response to the whole "Well it's fantasy so SE can make the girls warriors small and petite and it not matter because it's fantasy too!" but there's a certain skeevy-ness to that sorta logic that I'd hope SE would stray away from, particularly in that it really relies on the same sort of logic and rhetoric to justify sexy armor for women and the whole "Strong Female Characters" trope (Look up Kate Beaton's Strong Female Characters for examples of the issues with this trope presented in a funny way!).
The point with not accepting it is maybe SE will hopefully realize relying on tired reused tropes are annoying at least some fans, and either make additions so we can at least make the individual character seem unique (Say with the Au Ra, give the Xaela more neutral emotes and give them the option to be taller) or make the next race something less samey in terms of fantasy tropes. Also I'm a little bitter because this will probably be the only thing close to a reptilian race (Whether or not they're actually demonic or reptilian is irrelevant because I'm sure SE feels like they hit that "Demibeast race with scales" demographic) we've got and I'm massively disappointed with on the visuals of the girls. Like.. Would the same logic of just accepting it due to the way things go work for anything else in the game? RMT, dungeon mechanics, 1.0 to 2.0, jobs that are too weak or not strong enough, et cetera. SE has proven that they listen to fans in some regards (Heck, actually being able to look at Titan Egi hold aggro in dungeons with full parties makes me so happy), so I could only hope that in 3.1(Or whenever) that they'd add the addition to make it so I could crank up the height or change the horns without changing the face with the Au Ra (Another suggestion that I've seen pretty popular that SE hasn't commented on yet >.> )
Anyways, night Cilia! Enjoy your dark knighting, I've really enjoyed the story so far, and I hope you do too. Gonna head to bed myself, got school and work then busy times saving the realm later!