I should start this by saying that I am not demanding the waistcoat be unlocked, and I have male alts to enjoy it on, but I probably would make a nice steampunk MCH outfit for Aurelie if I could. With a skirt.
I actually think it has worse clipping than the princess dress - not in terms of how much is swallowed up by it, but how avoidable it is.
If you want to make a big puffy princess skirt, there's no way of doing that without it clipping.
But the Valentione dress could avoid clipping altogether, at least for races without tails. Make it just an inch or two longer so the ruffled hem is below fingertip level in a neutral pose, and it wouldn't be an issue.
You're making a huge assumption, unless you actually have quotes from the "same poster" being dismissive in the past, then demanding gender unlocks now.
I've previously argued against the view that female characters get all the good glamours. There are lots of nice things that are either exclusive to male characters or look better on them.
The "fantasia into a girl" argument is silly - and if anything is going to further drive the people in charge of this to say "our data indicates that people like playing female characters, so we'll cater more to them".
I think the Songbird outfits are a lot more balanced in making "similar but distinct" gendered versions of the same look. There are still reasons why people might prefer the other version for personal style, but you're probably going to use both in the same way, for the same sort of outfits.
The Valentione outfits just don't match in the same way. The male version is something from the 1800s / early 1900s / formal wear. You could use it for a wedding suit. Meanwhile the female version is.... cute and frilly. I don't even know what you could say it's from besides that. The only thing that makes them counterparts is that they were released together and both use the same two-colour effect.
Again, if the dress had a blouse under it, I think it would make a big difference to the apparent style of the outfit and what you could use it for, even if you didn't change anything else.
For me at least, none of those are an equivalent style. They're all long-sleeved coats, and from different eras. This is a waistcoat, not a "jacket", and you can't just substitute those other items for the specific look it has. We don't have that anywhere else that I can think of, except for the Lv80 goldsmith outfit which can't be glamoured onto other classes.
I think that's why people particularly want it - it's filling a gap for a 'basic' costume style that can be worked into a lot of things. There's nothing else currently available if you do want that look, except maybe the Boulevardier vest which is also male-exclusive.
I don't think that argument holds up. "Glamour this item that you don't particularly like, in the hope that enough other people will do the same that the devs work out this is a signal for them to make things that look like a different thing you do like."
I don't like the best man's suit. It looks masculine on a female character, and I'm not really fond of the style even on my male characters.
(I don't personally want to put my male characters in dresses, so I don't really have an opinion on the 2B dress - but again that would rely on people liking that particular dress enough to wear it in the vague hope it might lead to something else being unlocked in future.)
I think a lot of the draw of the waistcoat is that it isn't specifically masculine, but that it's an item that (in reality) can be worn by either gender, and with little difference in the style besides the tailoring and small details like which way the buttons do up.
If you took the Valentione waistcoat as-is and paired it with a skirt and heeled boots, that would look like a woman's outfit.
It comes down more to (modern Western) society's overall view of clothing. You can try to draw a line between "men's clothes" and "women's clothes" in real life too, but you end up with the same situation. Pants are men's clothing, skirts are women's clothing - but a woman can wear pants without people thinking she's crossdressing, whereas a man probably can't wear a skirt without giving that impression.
Back in the game, as someone who does stick to gender norms when picking outfits, I rarely-if-ever come across anything female-exclusive that I want to put on my male characters, but there are a number of male-exclusive things that I would like for my female characters, or that I do use from the unisex 'male counterpart' sets - just simple things like the Thavnairian gloves and sarouel, or the sailor brais, or the gambler's boots. I'd be disappointed if I couldn't access those, but I'm not at all bothered that I can't access the female equivalents on my male characters. I'd consider them female-exclusive at a mental level even if they weren't inaccessible.
More freedom is good of course, and if they can unlock everything for the people that do want it, that's great. But for now, that's the logical reason for at least part of the imbalance in male and female outfit availability: it reflects an imbalance in what people see as male and female clothing, and what they want access to.