Have no clue what this means - you can pre-compile for target platforms and therefore "fully" use whichever Apple device CPU.
However the EU decreed that it must allow for fair competition, leading to it claiming that it will enable JIT for authorized developers: https://developer.apple.com/support/alternative-browser-engi...
But I'm not sure that they have done so...
Mozilla: https://github.com/mozilla/platform-tilt/issues/3
Chrome: https://issues.chromium.org/issues/42203058