Good question, though I can imagine they took this action for two reasons:

1. They don't have the ability to freeze repos (i.e. would require some engineering effort to implement it), as I've never seen them do that before.

2. Many distros (and I assume many enterprises) were still linking to the GitHub releases to source the infected tarballs for building. Disabling the repo prevents that.

The infected tarballs and repo are still available elsewhere for researchers to find, too.