I think this regulation that comes into effect February of next year concerns all kinds of batteries, not only those of smartphones https://eur-lex.europa.eu/legal-content/EN/TXT/HTML/?uri=CEL... . I think, because I didn't doublecheck right now further than reading the first matching "appliances" paragraph (ctrl-f).

What I know off the top of my head, from reading the legislation a while ago. Is that technical reasons, such as waterproof devices, will still be able to retain non user replaceable batteries if it is needed to keep the device waterproof.

Especially vaping devices. Cigarette butts were at least easier to dispose of than these plastic encased tips and single use vapes.

I don't think single use vapes were ever compliant with WEEE, it's just that it's not enforced.

it's insane to me they designed it to be higher cost(li-ion + usb charging + oled screens!) than just using disposable AA batteries.

It should be helping you to understand just how absurdly cheap per unit a commodity consumer product is.

Vs how much you pay for it.