[lemax]

It works because you put your watch on, unlock your watch. Your watch remains unlocked until you take it off. I was under the impression if you’re wearing your watch and it’s unlocked, and then you pick up your iPhone, it acts as the key to your phone.

[valine]

The watch will only unlock your phone when you're wearing a mask. If FaceID doesn't see a mask it will ignore the Apple Watch.