I don't think ARM cores doing system management stuff that's not exposed to the user as a general purpose CPU really counts. But those SoCs count for sure, I didn't know they made those.

I assume the question is why AMD is not making EPYC or Ryzen processors with Arm cores for the application processors.

AMD continuing to have the Xilinx line of FPGAs with some Cortex cores and having Arm management cores that run firmware doesn’t really address this.

AMD said in 2021 that they were ready to build ARM chips[1], but honestly, I don't see the market for it. AMD could put an ARM frontend on Ryzen (and various interviews said they've prototyped it), but I don't think it would make a significant difference in compute/watt or whatever other metric, and there's not much in the way of ARM only software that people want to run. Maybe macOS, but you can still run that on amd64 afaik.

amd64 is still the default platform for desktop and server software. You can have arguments about the ISA, but for the most part that doesn't actually matter; amd64 is good enough, upstart cpu makers choose ARM not because it's better than amd64, but because it's at least good enough and licenses are available.

[1] https://www.tomshardware.com/news/amd-we-stand-ready-to-make...

Also worth noting that AMD is doing quite well on the server market with the c cores in terms of compute per watt over ARM options.