Do they? It might have been true month ago, not sure right now.
Now I'm not saying AI can't write ASM. I'm saying that compilers have a hard job. They output bad assembly, because the task is difficult.
Again, to the OP's point, look at any of the ultra optimized video codecs. You will often find hand rolled assembly to squeeze out that extra bit of perf; having the compiler do its job would probably emit something that does the job, but you can absolutely spend the extra time to do it yourself and do it better.