For something like a smart ring, a user-replacable battery is just totally impractical. Particularly if you want any sort of water resistance. The thing is just too damn small and will require special tools no matter what.
I don't think it's at all reasonable to expect such a product to have a user-replacable battery without doubling the cost. Sure it'd be nice, but the reality is sometimes it just isn't possible to accommodate.
The regulation is not some bureaucratic nonsense, it exists for a reason.
If its existence means the manufacturer has to do more work, and the cost might rise, that is considered worth it.
They can lobby to have the regulation changed, and regulations have changed in the past based on industry input, but saying "it's too hard" does not make the product suddenly legal.
I don't think it's at all reasonable to expect such a product to have a user-replacable battery without doubling the cost. Sure it'd be nice, but the reality is sometimes it just isn't possible to accommodate.