If it's crap ... We'll tell you
Couldn't agree more, Cthulhu!
Stephen, try not to add too much logic to anything fictional. The whole idea of anything fictional, especially sci-fi/fantasy, is to break away from reality and enter into something abstract. It's not about how exactly this alternate reality could possibly exist, but rather WHY it was set up the way it was.
While watching the movie I felt the same way. I thought it should have ended with the two main characters freezing in their last kiss...
But the whole part after that adds a whole lot to the movie if you think about it. When I watched it the second time that whole "what-if" thought-experiment during the last few minutes was actually the most interesting part of the film.