They did admit it in Selen's termination letter, and iirc only two talents period did not retweet the video. As far as that's concerned, I don't know any specific reason why if there is one, but no number of retweets indicates anything about whether or which talents had access to their accounts - at the end of the day, any idea that relies solely on what twitter interactions happened is shaky at its core becuase it now has to assume unsupported that the talents are in control at any given time.
This is why dishonesty used to be one of the worst things you could do. A liar once is a liar always, and acting like they're telling the truth is free game for you to get punked on.