It's almost as if you haven't read this thread in its entirety...
Ask yourself this when you start going on with those tangents. How many of those bosses can you have both the figure for in real life, and how many can you actually cosplay as? Let me know the next time you're able to sprout two extra arms and bulk up your entire upper body to cosplay as Sephirot. Because that's a key difference between the masculine and feminine bosses in FFXIV, that one side is still plenty relatable as a human, while the other is grossly over-exaggerated.
The problem being exactly that. The target audience, and, in relation to that, the context. MMOs in particular have always had an abundance in male gamers over female gamers, whereas romance novels have been more readily accepted by female readers than male readers. Is it a social construct? Or is it something in our biology that makes the two different genders separate in its ideologies? Who knows. Why can only females participate in sychronised swimming and rhythmic gymnastics at the Olympics? Why are construction and mechanical workers predominantly male? Context is very important when we talk about the 'ideal' population for a male or female.
However, in this forum and topic, we are dealing with the gaming context, which constitutes of mainly males. There are obviously men who like the appeal of a masculine body (me included), but the way game industries work prove otherwise. As someone stated before, the one time SE tried making a male less modest in Mobius was instantly met with heated backlash. Things will change in baby steps, however.
Of course, if you're able to cosplay as any of those, more power to you. What it comes down to it is the relative ease, and thus, the more relatable one is to a human figure, that the one being cosplayed is. You mention Garuda. I would say Garuda is far easier to model than Sephirot, as many of Garuda's extra features are not in anyway part of the human body. The only thing Sephirot has that is not part of his body are his wings; his two extra pair of arms, the incredible bulk on them, and demonic features make him already harder to relate to than Garuda, as a humanoid. Key of note that the topic title is 'women', not 'females'.
Yes, people don't cosplay Scylla. Or Belladonna. Or Melusine. Or any other beastial form that will make it impossible to cosplay as. However, there are plenty of Shiva and Garudas. How many people have seen as Xande? Sephirot? Titan? Diablos? Very few, if any. So yes, as much as you post enemies with muscles bulging out of their skin that in no way relatable, I will also make my restrictions based on what typical people can easily relate to. You can...as you say...'leave' with your weak, unrelated, incontextual images and arguments.