I tested several devices wearing them on the same hand during the night and got different sleep tracking results. In particular in sleep phases detection. The movement diagrams are almost the same, but deep sleep in % is significantly different.
Please take a look at the screenshots: Garmin VivoSmart 4, TicWatch Pro 3 Ultra and Xiaomi Mi Band 7
Could you commend on this why is this happening and what is the best device to receive most accurate sleep phases tracking?