We're not necessarily talking about "pop the back open and slam a new one in" batteries a la Nokia 3310, but rather being able to replace a battery at the end of its lifecycle without special expertise and tools, but still, with some amount of effort required.

That's the requirement at least, but companies are of course free to choose either approach.

According to a draft version of the ecodesign regulation on the EU’s website, batteries should be replaceable “with no tool, a tool or set of tools that is supplied with the product or spare part, or basic tools.”

https://www.theverge.com/2023/6/24/23771064/european-union-battery-regulation-ecodesign-user-replacable-batteries