> How would that be different if they didn't have a device? They would have died anyway, right?

Maybe. If they think that the device will help them in their hour of need, then they may be taking chances they normally would not have. To have something remote brick and then not tell the people that it was bricked is a gigantic ethical violation.

> Does the Apple watch not work?

Not to a medically relevant level:

"Apple Watch cannot detect all falls. The more physically active you are, the more likely you are to trigger Fall Detection due to high impact activity that can appear to be a fall.”

https://support.apple.com/en-us/HT208944