It's more about "Why does Riot feel the need to publicly kick up a shitstorm?"
It doesn't stop the fact that TSM "signed" Lustboy. It makes people think TSM is inept (which, frankly, they are but Riot shouldn't make a point to reinforce that), especially with how the tweet was worded. He didn't say "yet". He made it sound like Lustboy had already failed his check and wouldn't be allowed to play, when he actually meant that paperwork hadn't been filed yet and the behavior check still had to happen.