You can already replace your own iPhone battery without any technical expertise. I hope the law is more specific than that, because there are many things OEMs can do to comply and still make it a giant pain in the ass to do.
I've replaced multiple iPhone batteries with only a YouTube video. The problem is that the glue and placement can be a complete pain in the ass and user replacement voids warranty. Hopefully the law specifically states that user replacement should have a certain level of ease and does not void warranty.
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.”
You don’t seem to know it, but nebulous jargon like ‘technical expertise’ can be applied to anything like using a microwave so Apple includes instructions. Not seeing how this invalidates their point
They provided a kit and step by step instructions. It remains to be seen how they handle it, but don’t be surprised if they argue they already comply if that’s how the language of the law is written.
Most people can't put on a screen protector properly. I wouldn't perhaps go as far as claiming replacing iPhone battery takes no technical expertise. It's not hard but not quite easy either. In the case of iPhone there's also that even if you do it properly the device still detects it's not the original Apple approved battey so they limit functions on your phone such as battery health, true tone etc. New MacBooks does this aswell.
Technical expertise includes really basic things like being comfortable using a screwdriver on delicate equipment. Lots of people lack that level of expertise.