It’s not, as long as you’re using a recent CPU architecture. I think the slowdown problem was mostly related to Intel’s first version of AVX512, and the underlying issue has since been addressed (at least to the point that it’s not nearly as much a problem as it used to be).

This is also why it’s impressive that this is only AMD’s first attempt: it appears to work really well, where it took Intel multiple attempts to get it working well.