For a movie to be considered "a success" it needs to make back both upfront budget costs (production) and hidden costs (marketing). Marketing tends to be in the same range as production cost (which most studios don't actually admit) so a movie with a 100 million budget making 200 million is considered a flop. It needs to make over 1.5x of it's entire cost to be a success. Don't believe me? Well, a great example would be John Carter (250 million production) which reported losses of 200 million after earning 280 million. So this movie would need to do 150 million to be considered a success. That sounds like a small number, but it is actually pretty hard to accomplish with a comedy that isn't animated or a sequel. It's even harder to accomplish the longer a movie is kept on the shelf.
I'm sure you're wondering what this has to do with your statement about PR stunts. The thing is that box office growth is actually a small percentage of a movie's actual monetary pull. Most of the money comes from licensing deals; t-shirts, shorts, product placement, DVD distribution, lighters, underwear, special edition box sets, etc. That's where studios really make their money. A movie that isn't coming out is not generating licensing deals and isn't making as much money as it could be. Furthermore, Holding it back indefinitely isn't good news for shareholders who aren't in the loop.
So yeah, holding this movie back as a PR stunt is disastrous for a studio that just spent over 80 million producing and marketing this movie.