Safari is also just one of the forks of the KHTML/WebKit/Blink codebase Chrome is based on. Admittedly they probably implement some of the stuff they do implement themselves too because the common ancestor version is quite a long time ago now.
Meh, with games we want them to work independent of which type of controller we use, but display each driver's specific button graphics as needed. I see no difference here. Do I want dynamic upscaling and auto-HDR for all graphics cards? Sure! Do I still want it optimized for each type of graphics card unless the hardware makers can - unlikely - present a unified API? Of course I do.