Does it really? I go between an ICE car and my EV every 2-3 weeks and switching between the two isn't much of a mental challenge. I just prefer OPD.

I wouldn't suspect someone switching every few weeks would have a problem.

Other cases will arise: someone driving nothing but one-pedal for 7 years, suddenly finding themselves without it.

There are going to be new drivers who learn on one-pedal and drive nothing but that for years, so all their core habits are formed around that.