I am trying to stay away from this thread for the sake of my own sanity, but just to add this since some may be interested.
I noticed this earlier too but I didn't look up the concept art until now. An example of the reverse of what tends to happen where female characters are covered up for even minor skin exposure, and I hate it too. In-game the male version of the Githyanki armor has ugly white baggy pants which compromises the design, I dunno why they changed this with the male version. The pants on the male version looks totally out of place imo...
I wish the devs would make the male version more accurate to the concept art too.
Going by the texture names, they may be different sets of armour: the female version is "Githyanki Halfplate" and the male version is "Githyanki Astral Plane". I'm not sure if that's just the way it is (both models have the same name) or whether we can expect to see male & female versions of both. There are some indications that the armour is still unfinished.