Epitech Alumni here (42 is basically the same thing but free). The idea is rather that if you start from low level programming it is not difficult to go up, and you can pretty much do anything after that. I do think that starting from C/C++ & having a good understanding of how any interpreted language work makes you a better web developer. Not that it guarantees it / is absolutely necessary, but it gives you a broader understanding, and that's what the founding team from 42 believes too.