So that's dozens of events where they have to send first responders out to see if there's a serious injury/fatality on the mountain because it could be nothing or you could have collided with a tree or fallen off a cliff.

The problem seems to be that Apple under-thought this feature. They made it one-size-fits-all instead of context sensitive. For example, maybe when it detects you're near a ski resort it asks you to switch into a skiing-friendly mode for the rest of the day. Same for amusement parks and other common pastimes that involve rapid deceleration events.

Just because this number sounded low to you as quoted in the headline doesn't mean it's not a big expensive problem for them. They can't ignore 911 calls.