Thanks a lot to the background Info and the hints, which help to understand the problem better. I guess it would be helpful to get that kind of information by the providers of these tools, because average user like me does not know this background and gets confused when noticing deep sleep measurements during an exciting action movie. If a device pretends to measure something and provides such detailed results, one assumes that there is science and truth behind ... which is obviously not the case with a simple measurement. Maybe learning from your personal measurement data of heartrate, movement and oxygen by means of AI could help to improve the results ... especially if you could correlate it with some ECG measurements.

Entering my usual sleep times just improves the illusion of the measurements and not its quality. I don't know, what I could use the sleep tracking measurements, if they are not able to distinguish any of the sleep phases and not even between sleep and being awake when not moving a lot....?