You understand git. If someone said you need to know how sed works, or grep, or babel, or clang, or bash, or perl, or literally any other tool that you use regularly that you don't know the internals of then you'd quite reaaonably say they were wrong because you're an expert what matters to you and you can do your job without knowing how something else works. Perhaps you should try to respect that other people choose to become experts in things that aren't git.