Each vendor. Intel BLAS (MKL) has Intel-specific optimizations and AMD BLAS has AMD-specific optimizations.
Intel is still acting in bad faith by allowing MKL to run in crippled mode on AMD. They should either let it use all available instructions or make it refuse to run.
The latest oneMKL versions have sgemm/dgemm kernels for Zen CPUs that are almost as fast as the AVX2 kernels (that require disabling Intel CPU detection on Zen).
Intel is still acting in bad faith by allowing MKL to run in crippled mode on AMD. They should either let it use all available instructions or make it refuse to run.