[As of logging in today - never before now, not even on 6.3 launch day - pressing start has started toggling moving my mouse with the left stick, including on the title screen. HOW DO I STOP THIS FROM HAPPENING. It's extremely annoying, I can't find how to turn it off, and I never wanted it to start happening in the first place!
And no, changing main menu mode from controller to mouse didn't help, and neither did turning off virtual mouse. I can't find any other setting that would be relevant.]
UPDATE: It wasn't an FFXIV problem, it was a "bluestacks started doing this today without telling me" problem