I'm thinking there's a possibility Jean is a save-scummed revival from like pre-Dark Phoenix era. That would fit how she's being written, but it would also give new context to certain very small scenes. Like her interaction with Brocolli kid: Is she making amends? or is that history just lost on her entirely? The line she repeats to Storm: Is she actually repeating it? Or is it, as far as she knows, the first time she's said it? Storm laughs, but Storm could be in on what's really up as she's obviously respected as a priestess of a sort.
I was thinking about this last night in relation to how people keep saying the character writing is "off" because if you look over every issue so far... that's largely just not the case. The obvious standouts have been Magneto, Emma, and Sinister - big surprise, Hickman considers all three favorites - but Scott, Logan, Kurt, Mystique, Apocalypse, etc.? The guy's written like five lines for M, but he clearly gets her voice. There's obviously more to X and my Jean theory is above, but yeah, I pretty vehemently disagree that the dialogue is off. Most of these characters don't sound any better or worse than do under anyone else's pen. I think Hickman is just portraying them in the new status quo being set up as finally being empowered to see the world as it is and, rather than assimilate, make their own way within it.