I also don't see why an Apple Watch wouldn't survive all those mentioned things. Pretty sure I did all those things with an Apple Watch on, except for the specific 108 mile gravel race. But I don't see why it would fail that.
And both might absolutely scratch while climbing, and if you're unlucky and hit it in the wrong spot, also crack.
That said, if I were an athlete in any of those categories and did it all the time, I'd still absolutely choose a Garmin.
But, Apple Watch Ultras and also Titanium models since Series 6? ship with Sapphire crystal too.