There’s a hit that comes from “frequency scaling” on avx512 and avx2 instructions on Intel (worse for 512), so a total of fewer instructions isn’t always worth it. IIRC, AMD doesn’t pay a cost for avx2, but I don’t know how it works.
The problem with the AVX2/AVX512 clocks with Intel is not the fact that they must clock lower to use them (for pure AVX code, running wider but at the lower clock speed is still worth it!), it's that they need to clock lower pre-emptively for any such instructions, and must remain at this lower clock for a while. This means that code that executes a few AVX instructions every now and then mixed in with a lot of integer code needs to run the whole program at a lower clocks.
In contrast, AMD runs their chip power supply from a huge mimcap built in the chip, meaning that they have margin so they can start executing exceptionally power-hungry instructions, and only clock down reactively if it's actually needed. And also do the clocking down and up with a much finer granularity, clocking up immediately after the need to clock down passes.