>If we assume C is the ‘fastest language,’ whatever that means

I agree that it has no meaning. Speed(language) is undefined, therefore there is no faster language.

I get this often because python is referred to as a slow language, but since a python programmer can write more features than a C programmer in the same time, at least in my space, it causes faster programs in python, because some of those features are optimizations.

Now speed(program(language,programmer)) is defined, and you could do an experiment by having programmers of different languages write the same program and compare its execution times.