That's what I mean though- in the Core 2 Duo vs K8 / Athlon days, Intel was much slower for denormals and subnormals than AMD. I'm not sure why but I thought this was common knowledge.

This is true on most hardware. Running ftz on H100s or B200 gives a free 10-20% boost for GEMM-epilogue workload

This is true only on most hardware that does not care about computational errors, i.e. which is intended mostly for games or for AI.