Literally specifically said that. Yet Edge and Chrome on iOS actively suppressed JXL in prior builds (yes they can do that — actually calling it a skin is technically wrong as while the engine is Safari, they have a lot of flexibility), and very recently exposed it.
Apple is dropping requirements for all browsers to use WebKit, but that doesn’t mean Mozzila/Google/Brave have started releasing them, especially with iOS 17 still being a beta.