The sleep app a real challenge to get right. One significant reason for many. More then one person in the bedroom and even more important same bed. The watch senses movement, and noise, plus vitals. All impacted by another person. The other person moves, gets up, all the above can easily respond. Sense the movement and the heart rate will move a few points. Thus, giving a false reading of sleep at that point. Go from deep to normal maybe.
Been using a Watch app for sleep for two years. Works well but the daily results not always aligned by how I felt from the nights sleep. Upon analysis, the other person has a greater impact on the results then my original thoughts.
To get it right, two bedrooms.😂