I’m not sure what the name for this fallacy is. Appeal to unrelated concept?

Among the first functions children learn are things like addition of two numbers which lack this supposedly natural property.

IMO you mistaken math-like infix notation with the number of arguments function receives.

  Tuple(Number,Number) -> add -> Number|Overflow

Depends how you imagine a function. Just imagine it like a funnel. Your argument is honestly at the very least irrelevant.