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.
There are diver watches with replaceable batteries. Probably most of them in fact. The reason these irreplaceable batteries became popular isn’t because they’re more waterproof, it’s because it’s just easier to do. Still perfectly possible to have decently waterproof phone with a replaceable battery. It’s not like we didn’t have such phones back in the day.