The fall detection on my Apple Watch is so rubbish. It’s gone off twice; both times when I’ve been playing with my dog, and remained upright on two legs.
On the other hand I have fallen so many times. Fell off my bicycle a couple of winters back, got a massive bruise that took like six months to fully heal. Slipped on some ice and tumbled down a cliff. Slipped on a patch of ice and slid down a hill, completely ruining one pair of trousers.
There’s countless other smaller falls in there, like one literally last Thursday where I hit my head and got a nasty headache for the rest of the day.
None of these occasions ever triggered the fall detection.