Garmin originally put a pulse oxygen sensor in their watches for mountain climbers. A Fenix was the first to get this feature, it's marketed as the hiker's watch. Peak bagging is basically a continuum of hiking. People can be affected negatively even at low altitude.
There was a lot of interest in whether blood oxygen saturation could provide early warning for covid infections. The data says not really, it turns out that if your watch does respiration rate that gets you closer to a covid pre "diagnosis."
I'm not sure what other value the data might have?