>> people don't copy the speech of people outside their group who they don't identify with

I don't think this is true. Words and phrases from specific sub-cultures filter across to the broader culture all the time.

Example: bling, hater, player, stan, flex all had origins in Black hip-hop culture but now are used generally at least in the U.S.

That's because Black hip-hop culture was deemed cool and worthy of emulation. I'd be surprised if people knowingly copied AI's speech style unless they really like it.