Well, ML-KEM has zero assembly and was written entirely from scratch, for example, so it must be more than you'd think if you think we "reuse the same machine code for this that you'd find in everybody else's implementation." In fact, almost everyone else's was found to be producing a variable-time DIV instruction, while ours was unaffected.

Porting the assembly to higher-level generators has nothing to do with lawyers (??), the goals are stated in https://go.dev/wiki/AssemblyPolicy.

The idea that one day we'll write All Of The Cryptography Code Once And For All In The Perfect Language and reuse that across languages comes up pretty regularly, and has never panned out.