And just how is max(a,b) good code and max(b,a) bad code?

Because the alphabet goes a, b, c, not b, a, c. The lexical ordering is uniquely privileged both when reading and writing.

Code written for one will fail for the other, and negates the whole point of interoperability. Therefore the method signature should not be copyrightable

Beware interpreting copyright law with the assumption that interoperability is relevant. The law doesn't care.

copyright has a fair use clause, which states that one can decompile software to produce a derivative for the purposes of interoperability. This then must assume that any apis being implemented has to both fall under copyright (otherwise, this law does not apply to api), but also means that the law allows for the use of the api for the purposes of interoperability (and therefore, you cannot claim to have the sole rights to an api).

Beware interpreting interoperability as a form of fair use. I wish we could make that assumption, but I don't think it's warranted.