That's actually one of the most reasonable takedowns I've ever seen on github. It was clearly written by a human (ignoring the boilerplate) who had bothered to actually look at the project and at how git[hub] operates ("forks", "branches").

Normally it's just a long list of URLs flagged by a bot then sent without ever having a human look at it.

Yes, it's very well written, except for the only sentence that matters, which is a completely unsubstantiated claim of infringement that has nothing to do with the rest of the letter.

Perhaps the spent some extra time making this look pretty because they anticipated a bit of scrutiny?

Apart from the fact of being completely substantiated of course. But hey, don't let actual facts get in the way of your opinion.