Not sure if this way of comparing programming languages (i.e. do A in language X and do B in language Y => Y is not slower than X) makes enough sense to draw conclusions. If you can use clever algorithms, in the majority of cases you'd do so in any language and in the majority of cases C would lead to more performant code than Python. Then again, wheteher this matters in the scope of the actual application is something else.
I suspect his comment meant to imply that a level of skill exists for which a programmer could build an FFT in python, a plain DFT in C, but not a proper FFT in C. That programmer would benefit from using python.
