Does the process take a long time before the account gets removed?
I would say anywhere between one to three days. My experience with GitHub support has been quite good so far, I think I have taken down 3 or 4 of those fake ones. HyperCash-HC was removed within 24hrs of my report.
Make sure your report has all the details, you need to include links to both infected wallet and virustotal. As for MultiVAC, ask TakeItEasy to test their latest two repository uploads - "Core" and "Release". Report these two.
Edit;Update: May 21, 2019, GitHub is taken down!