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.
Water resistant phones existed before the trend to glue batteries in.
Also digital watches often offer water resistance suitable for high depths since a long time and always have had easily replaceable batteries.
So I am quite sure there will still be plenty of water resistant phones, although they may get slightly rarer as it is more difficult and thus costly to ensure tight seals on removable parts than to simply seal it with glue.
Yeah but with your watch example to retain water resistance you need to take it to a jeweller to do it properly. This is not “user serviceable”. You could also argue that they are already user serviceable as it’s currently possible to replace your own battery with a new battery and a small toolkit and instructions; how they will choose a level of difficulty will be interesting