It's also showing various sleep stages whens he knows she's been awake, trying to sleep.
To be fair, people actually aren't that great at detecting when they (or others) are really sleeping. Especially for one's self, it's common to believe that you spent more of the night tossing and turning than you really did, when in reality you actually got some light sleep sprinkled in those periods.
That said, consumer-grade wearable devices are demonstrably not great at this either.
But it never showed any naps as actual sleeping time. Until I saw your comment I thought that the garmin would only log sleep overnight and never during the day. Did you have to enable something for it to log naps?
The Garmin may be right considering the quality of TV... even if she had her eyes open...