Is this level of device ownership actually desirable by EU powers? Replaceable batteries enable all consumers, device rooting only a very small subset.

I would fly to Europe to buy my next phone if it ever happens though.

Device rooting isn't only of interest to developers. It also allows anyone to bypass the arbitrary rules set by Apple/Google on what software you can run. That's of interest to the whole population, even those who only use the app stores because it increases competition with the app stores.

Us hardware EU software is an excellent stop gap until full digital autonomy.