I'm sure the Apple Watch is more accurate, but I find it hard to believe that to be that more accurate drops the battery to by a factor of 20. My hunch, as somebody who used to work at Apple, is that the watchOS is no different than any other software and is very far from being optimal.
YOYOZO, my game that received a "Best Games of 2023" accolade, was also written in Lua. It is only 39KB despite containing two music tracks, physics and particle systems, online high score board, dynamic sounds, two fonts, a tutorial and more. https://news.ycombinator.com/item?id=38372936