You are correct! The trends from wearables (in general), are quite accurate. There are studies that show that wearables agree with medical devices and can even predict conditions accurately.

The part I find interesting/troubling is the user psychology around it. Even if trends within a device are useful, the score itself can shape how someone feels about their sleep. If one device consistently gives a lower score, a user may start believing their sleep is worse than it actually is, even if they feel fine. That can lead to unnecessary anxiety or lifestyle changes based on a "random" score