The tainted supplement is irrelevant. Everyone knows there are supplement companies that are reliable, and using something questionable is on you. Nothing is stopping fighters from obtaining known tainted supplements that they can send in case they piss hot.
CSAD is not a serious organization; it was setup by the UFC as this supposedly "independent" testing body, which is a joke; it amounts to an organization investigating itself. This is a token roid bust to make sure it looks like the UFC is doing something about PEDs when they aren't.