Even Shakespeare used 'they', though I suspect, while gentleperson isn't a neologism, its use is probably anachronistic. As most uses of the word 'gender' are in period pieces.
There's nothing new under the Sun. Take
Thon for instance. Instead of trying to second guess these things, just understand everyone's vocabulary is peculiar and idiomatic to themselves. We're constantly trying new things out, they either thrive, die on the vine; or become fossilized as a kind of political statement.
I think more apropos, culture is usually pretty static in fantasy, the one in FR seemed pretty staid at least, it isn't a living entity because it's supposed to take on a life of its own after the fact. Which is why any kind of shift in the world undergoes this kind of scrutiny. It doesn't help that WotC has been pretty up front that these changes have little to do with any artistic impulse, it's to make D&D more marketable, or at the very least, stop it showing up as the butt of so many clickbait articles.
I think a VP recently said that Dark Sun has been shelved because slavery is too problematic a concept to deal.