The "researchers" jumped the gun. AMD hasn't even had time yet to reproduce them for verification purposes.
When Specter and Meltdown went public, it was huge news because despite having six months to work on it, they weren't even close to fixing it. Even if one of these 13 ends up being legit, it most likely could have been quietly fixed without any fanfare. In this case, everything the "researchers" did was about maximizing fanfare. That should concern everyone. I hope this doesn't become the new norm but it could.
Well I agree it's very very poorly executed if that indeed is genuine security firm. But looking on employees backgrounds, I have hard time to discredit their expertise in security.