Yeah, that’s not quite right. You need a means to discuss things and review code. You can do this via a website or mailing list. The Linux kernel uses the latter. Lots of other devs use the former. Like Github. And Github and Git aren’t the same. The issue tracking, discussion platform etc are something Github does on top of Git. You can as well use Email or a different service/online platform for the communication. The actual program code is stored in Git in both cases.