[jerlam]

Most sleep trackers have similar issues. For example, most won't detect biphasic or polyphasic sleep correctly - it's assumed that sleep happens in one unbroken period once per day. If you get up in the middle of the night for a snack and then go back to sleep, it's a coin flip whether it will be detected as the "end" of sleep, or as a long "awake" period in the middle.

When I hit the snooze button on my phone and go back to sleep for another hour, both my Garmin and Oura are inconsistent whether that extra hour counts as sleep or not.

Garmin's even weirder than most as it asks you for your normal sleep hours when setting up the watch, which suggests that it's not as smart as it should be.

Garmin, to its credit, is slowly moving away from pure sleep tracking and using other metrics like HRV, stress, and yesterday's activity levels to calculate readiness for today's workout.