>... you still have a working phone
You do, but if Google literally dropped support of their phones, you'd never get another security update, so it'd be in your best interest to move although not mandatory like if Stadia shut down. The comparison is about peoples' visceral reaction to Google products when they're disappointed, not specifically when the product is dropped.
> What significant things are much better on non-Google Android phones?
Not my point and frankly I have no clue: I've had a google android phone of some kind or another since the G1, which if that reference is lost on you is the original android phone.