I definitely agree with you. Even my Garmin Phoenix 5x plus will last multiple days with GPS usage for Backcountry camping. Another factor I worry about is the durability of the screen. Although you should always travel with backup Maps nobody wants to lose their primary navigation tool because a touch screen is nicer than Sapphire glass displays.

That said the Apple watch is a nicer experience than the Phoenix which I don't tend to take out of the house too often outside of activities now. Indeed the Apple watch is claiming to be usable for recreational scuba for which the Phoenix is not and you would need to use an alternative Garmin watch

Perhaps the next iteration of the ultra watch will have features to extend battery life beyond the 60 hours in low battery mode it claims and hopefully towards 100 hours (14 hours * 7 days) of usage on low battery