I was thinking and once the seed was released players couldn't select the gender that they could play as, and that it was now done through reading a player's brain waves.
But I think that was always a feature since the nerve gear. And it's shown in the first episode from when everyone was changed to their irl self's, as the nerve gear definitely couldn't tell a users gender just from some body celebrations. As all human body's vary so much that for some users it may be hard to tell, pushing fourth the use of a users brainwaves from the start.
"yeah well a user could choose there gender in alo so then the nerve gear didn't do that", the whole of alo was build upon the same database and server as Sao, and the whole how people look in irl reveal was an 'extra event' that was done after character creation that was never triggered in alo leaving users to be able to select the gender of their avatar
But once the seed released a users avatar gender would now be selected from their brain waves like how it always did originally due to it being a cut down bare bones version of the original cardinal system from sao, removing any functions that weren't necessary for operation and would take up unnecessary space, this would be the avatar creation leaving people's avatars to be randomised and relying on a users brainwaves to select the gender for their avatars.
