From my understanding, sealant used to make phones waterproof is basically glue, which precludes "easy" replacement of batteries.

I don't think you properly understood my comment. I am specifically saying: even if replacing the battery makes the phone no longer waterproof, you can just not replace the battery. Nobody comes into your house at night and forces you to install a new battery because your old one isn't good anymore.

It's very nice to be able to replace a battery in the field. I used to carry a spare charged battery and swap it for an instant recharge. That use case is still valuable to me, but isn't possible anymore.

Yes, that is why I'm arguing that even if changing the battery must necessarily break the waterseal, the battery should still be changable. In this hypothetical scenario it would be worth it to leave it open to the individual.

I understood your comment. The article implies that the battery has to be _easily_ replaceable, i.e. that you could just take a battery and maybe a screwdriver out of your pocket and replace it.

I don't think it's easy to design a phone that would at the same time a) have easily replaceable battery, and b) be waterproof until the first battery replacement.

Why not?

Galaxy S5 did it 9 years ago