From the article: "it will warn of a potential issue rather than diagnose it"

Seems like lawyer speak for "please don't sue us if we get this wrong" but I suspect the ad campaign for this feature will suggest otherwise.

The reason they do this is that their algorithm makes errors, and setting it this way means they can tune for a high specificity (giving up some sensitivity).

The breathing disturbances notifications work in a similar way. They alert you to potential sleep apnea, but then you need to do an at-home or in-lab sleep study in order to get a diagnosis.