Looks like they are responding to https://github.com/intel/scikit-learn-intelex#-acceleration
I completely agree. I hope some Intel competitor funds a scikit-learn developer to read this code and extract all the portable performance improvements.
The point is that sklernex would bring performance for all X86 architectures, not just Intel. And yes scikit developers already working on generic improvements there
As @jjerphan commented above, there is already ongoing effort to get an improved portable brute-force implementation in vanilla scikit-learn, see:
(A jump that large suggests to me they may be fixing issues in the default implementation that could also be fixed for other processors!)