Right. GitHub seems to have made up a 1201 notice-and-takedown mechanism out of thin air, with this mechanism serving as Microsoft voluntarily doing favors for other big corporations rather than the fulfillment of some kind of legal obligation.

I find the GitHub announcement deeply unsatisfying for that reason: GitHub is unilaterally inventing a body of "law" that's going to meaningfully govern the lives of tons of developers in the future. This body of rules is "law" and not law because the entity doing the enforcement is GitHub and not some government, but GitHub still has enough power to cause injury if it decides it doesn't like you.