Agreed, in that the performance benefits you can get out of a higher level language will often depend on the stuff where the limits of human cognition is the performance boundary. As computing gets faster in general, the practical considerations should shift more towards the performance you can get out of an entire system than unit-for-unit performance. On that level, human comprehension often seems to be what needs to be accounted for.

I think of it as problem akin to how you can make traffic run better in an entire city rather than optimising the performance of an engine in a single car. It doesn't invalidate making more performant engines, but it's a different level of consideration.

When saying, "JVM is as performant as C", it's easy to run the numbers and see whether it's true or not, objectively. The caveat that GP throws in is, for the same amount of effort. Then you need to specify which human and under what circumstances, and the entire thing gets hairier.