It seems it wasn't a new release. It opened in Europe in 2017 to very low ratings, the film didn't cost very much to make (relatively speaking) and this stunt has brought more attention to the film than any advertisement could have on its own.
It has been available to torrent for some time. I can't think of a better candidate to try this experiment on. It worked fantastically. Beyond that I can't see this having gone unnoticed for 6 hours.
