There's a difference between a cover up and just not telling anyone in the general public that something happened, this wasn't a cover up by Souths & I don't blame Souths for not telling anyone either. Clubs punish players in house all the time without it ever being leaked to the media.
If anyone covered it up it was the NRL. Based on their (The 'integrity' Unit's) precedence set for anti-social behavior in public both players should be missing NRL games. I think it's more than reasonable to assume based on those precedence's that they've opted not to suspend either player because of the fact that the story would be leaked to the media. This shouldn't be surprising anymore though, the 'integrity' unit is purely there for PR reasons, it's become glaringly obvious that we shouldn't expect any sort of consistency, transparency of god forbid some integrity in their decisions.
As for the argument that Souths fans deserved to know, I think as supporters we all accept to some degree that for a football club to be run efficiently and effectively we're all going left in the dark about why certain decisions have been made and that's fine. You'd think that Maguire & Richardson have bought themselves enough trust with the fans through their service to the club that they don't have to release a statement every time they make a hard call within the club. And I'm sure ultimately that's the way the fans would want it to be anyway....