30 seconds to leave the theatre

Ok so just before the climactic end of the film there is a warning giving you 30 seconds to leave the theatre if you don't want to witness the potentially disturbing content to come afterwards. Is this a common feature when films such as this are being shown at film festivals and the like? Or was this something Gaspar Noé decided to put in the film by choice? I personally think it is a work of genius. That way viewers of the film should have no right to be offended by what they saw next, as it was their decision to stay and watch. I had already known to some extent what happened at the end of the film through some spoilers, but this warning message had me questioning whether or not I wanted to go ahead and see the rest. Although, I think it would have been pretty pointless to stop watching from there. The ending was great too. Just when you think you know what's happening it after its been shown so graphically, they pull another twist. Another great Noé film. I saw Enter the Void first, Irreversible second, and now this. Enter the Void is still my favourite film in general right now, however. Onto Carne and maybe his new film "Love" soon.