Benoit started doing the diving headbutt because he was a Dynamite Kid mark, long before McMahon was involved. I'm pretty sure that he didn't stop doing the move after the Kid's health went to shit. Has there been a tell-all claiming that McMahon forced Benoit to keep doing the diving headbutt?
Vinny Mac never told him to use the move since he had had it before WWE, but it is very, very, very, very likely he knew that Benoit was fucked in the head or that he had concussion issues while giving him the green light to perform and not even trying to help the guy/put him out for rehab. Resulting in the Benoit murder suicide. Hence the gif.
The gif does not tell that story, and even then you're making some leaps of reasoning. Bret Hart was perfectly capable of hiding his concussions from his employer, I don't see any reason to think that Benoit was less able in that regard.
He's responsible for many, many atrocities, but probably not this one.
The documentary about it discusses why I believe Vince had a role in how Benoit progressively got worse. I don't see a scenario where Vince doesn't know about it honestly.
With Hart, and with Benoit I suppose. Concussions had not been truly...known...at the time? Can't think of the right term. Sporting leagues did poor jobs of handling them, just ask the NFL. I am not saying it is Vince's fault 100%, but he, if not the WWE, handled the situation poorly. Benoit of course refused to tell them for his reasons explained in the doc as well.