It's just an instance of "No True Scotsman". What is fully qualified? There are certainly areas of programming where not knowing C is a deal killer, but they are a minor subset of all professional development.
And, yet, almost every program you use on your computer and phone has at least some portion written in C.
Yes, and my computer and phone run binary machine code through their smashed rock in which we put electricity. I don't know much about the smashed rock nor about electricity (more than high school level knowledge).