Apple has the Accelerate.framework already, which is hand-tuned per chip-type, and is what most of the libraries call into. I’d imagine a lot of work will have been done to make that as seamless as possible on the new chips.
It’s also kind of useful for a a framework team to be able to call up the guy designing the next cou and say that “this bit here is a bottleneck, what can you do for that?”...
You still need to recompile and relink. And it's not that simple, Apple's implementation of LAPACK is well out of date for e.g. - it dates back to 2009.
Accelerate is barely used on Mac for scientific stuff in my experience. People tend to use Intel MKL - see for e.g. the Anaconda Python distribution - all of the NumPy/SciPy libs are linked against MKL.
It’s also kind of useful for a a framework team to be able to call up the guy designing the next cou and say that “this bit here is a bottleneck, what can you do for that?”...