I did it myself with some kit bought online for a 2013 (I think it might have actually been specifically an iFixIt kit). Ungluing the battery took all of 15 minutes and the plastic card jiggering was fairly trivial.

I’m quite positive the actual reason for its high difficulty score is that actually reaching the battery basically requires completely dismantling the whole laptop — the battery is under the motherboard, and every little module has to be removed and taken out fully before the motherboard can go. And putting them back in, the connectors are ridiculously small and fiddly.

The battery being glued was completely a non-concern IME.

I recently did my 2013 MBP, and while it was a massive pain that left my hands hurting afterwards, I was able to do it without solvents or having to dismantle the entire system like iFixit said I would need to.

Probably spent about 20 to 30 minutes using some old sacrificial credit cards to break the glue & pry the cells out.

Huh, no, the hardest one was opening the first Google Pixel without damaging the screen. I did break mine by prying too carelessly.

Still, replacing just the battery ends up being a lot cheaper.