Here's my answer (as the founder of Pebble - both eras!) on this. We're a small company this time (standing on the shoulders of giants by using open source PebbleOS - thank you google!).
We are excited to make new devices, but wary about over-promising. We'd rather under-promise and over-deliver. So far, we have only received a few requests for warranty support for our first new watch (Pebble 2 Duo) and we have provided support for everyone who has asked.
Generally most sleep tracking products use actigraphy (measurements of your movement) to track sleep. Pebble partnered with researchers at Stanford back in the day to produce an algorithm for our operating system, which worked quite well and is now open source!
It has a hard cutoff built into the firmware at two minutes so after that point the recording stops and the ring turns off until the next button press.
This isn't a question I understand, but I appreciate you writing it. At the end of the day it's up to you - if you think this is useful, please use it. If you don't want to use it because of the 4.7 grams of e-waste, I do get it.
All consumer tech is intentionally disposable. That's life. Especially for tiny smart rings that are water resistant. It's a ring, it's going to get banged up, you'll lose it or smash it. It's new tech - there will always be a new version, etc.
Better to have loved and lost than to have never loved at all.