BocoDragon
or, How I Learned to Stop Worrying and Realize This Assgrab is Delicious
More likely, they're trying to justify their choice in canon specifically to justify it to critics. I mean, I really doubt the truth about Cortana has been held back for, like, a decade, until the perfect time to reveal it appeared. Likewise, Kojima hasn't bothered to explain the revealing clothing his female characters have worn until now.
I'll admit I don't know much about Halo or MGS overall though, so maybe I've got this all wrong.
There has never been a major character this naked in his games before.
Kojima is so famous for explaining odd elements of his game in-canon that he even has a meme about the phenomenon: "Nanomachines". He's always making up explanations like this... the difference is that this one taps into a controversial subject as of late.
I can believe that people at 343 are hyper-aware of the sexualization debate of the past half decade... but if this was their conscious response to it? They would have known it would go over like a lead balloon. I think they asked themselves why, and made up a reason for their canon... but in order to answer to critics? You wouldn't answer to critics with that.