I don't read German, but if the law does not require them to actually produce those batteries more than what is required for the initial run, then all they will do is come up with a proprietary battery format for every device and never make them. And yes, even if some form factor becomes popular (BL-5C, here we go) only dodgy suppliers would bother making compatibles. And for others you will never see a spare battery in your life.
You don't need to read German, the EU employs a
lot of translators. The draft and final regulations will be available in BG, ES, CS, DA, DE, ET, EL, EN, FR, GA, HR, IT, LV, LT, HU, MT, NL, PL, PT, RO, SK, SL, FI, SV, at:
https://ec.europa.eu/