"only recently released processors that met the requirements for the other haswell"
This is false. Zen was introduced in Q1 2017, before that patch was written and it already implemented all the useful parts of the Skylake instruction set (and also the SHA extension not implemented by Skylake). The fact that the CPU vendor should not be used when testing for CPU features was already discussed a lot, many years ago, so someone of the library maintainers should have noticed this bug and removed the inappropriate test.
About AMD not supporting yet AVX-512, that is far less annoying than the fact that Intel does not support AVX-512 yet in any of their CPUs which are actually competitive in their target market (Ice Lake is worse than Comet Lake, Cascade Lake is worse than Epyc 2).