Of course. Auto-vectorization isn't magic, for one. In any video codec, the hot kernels will all be in hand-written assembly.
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.
I find it hard to believe that the output of modern compilers is objectively 'bad assembly'.
They are not saying the assembly is bad all the time, but merely that sometimes, for some inputs, the assembly is bad. Which is definitely true, though I would prefer the term "suboptimal."
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.