https://mikestone.me/i-dont-trust-github [mikestone me] "I Don't Trust GitHub"
I'm not big on #GitHub (even before Microsoft bought them), but my impression of DMCA is that GH did not have any say about closing repositories.
The claims in the DMCA request may have been garbage, but #Microsoft GitHub doesn't get to choose. They have to disable access to those repos or be liable for any further damages the copyright abusing #RIAA claimed.