The last gen MacBook air disagrees. There is no reason that thing should throttle. My unbranded clevo 9th gen i7 does not throttle and that has a lot higher tdp than the 9w of the base MB air.

Sure, my laptop sounds like a spaceship when I'm compiling, but at least I am getting the advertised core clocks.

Edit: which is why I'm looking twice at the new MBP :) if only it would run Linux.