One goal was to have students graduate, so to speak, from the class actually having a GitHub account.
IMHO this is not entirely dissimilar to e.g. requiring Facebook for distributing course material, to which there are plenty of opponents. You should not need a Facebook account to learn. You should not need a GitHub account to practice computer science.
(Full disclosure: I do not have a GitHub account, nor do I intend to ever have one. I have taught some introductory CS.)