sure but the Oura does a bunch of unrelated stuff specific to health and also has to be charged twice a week? they're not even comparable products

I don’t understand what you don’t understand. The oura comparison is one they made and used “charging every day” as a reason to not use a rechargeable battery. If they took the oura hardware model and applied it to their voice recorder ring, you would be charging monthly if not longer.

TL;dr - There’s no reason to not have a rechargeable battery other than to create e-waste and “a revenue stream”.