It had been in the works for a while, but now it has formally been adopted. From the article:
The regulation provides that by 2027 portable batteries incorporated into appliances should be removable and replaceable by the end-user, leaving sufficient time for operators to adapt the design of their products to this requirement.
I mean rubber seals and o-rings exist. If I remember correctly the law doesn’t demand easily swappable batteries, but rather them to be replaceable at all. So just use screws to hold the backplate in place, it could even look somewhat cool like on a Royal Oak Watch.