Proven asm code like in TAOCP is safer than any other language. For example you know exactly what the FPU will do. Good luck with any compiler.

I know that is not what people mean with "unsafe", but it is getting tiresome.

TAOCP was written in different times, namely one where microcode was not a widespread thing. As it stands, your asm "proof" relies on having no µcode update. CPUs are no longer easy to understand like 8086s.