Personally, I doubt that. I would assume that GitHub just banned all accounts that were directly associated with the project as a precaution.

I think it was somewhat irresponsible to block everything. It hampers instigation of the repo's history. It's good that Lasse had another mirror.

Woops, too late to edit this comment and say *investigation

Or you know, they just reacted with a ban hammer on all accounts related to xz and to heck with innocence.