The thinking is that if they don't commit and make it canon, all the would-have-been foreshadowing becomes queerbaiting. (In the link I used when for Misha supporting Dean/Cas shipping, this one, Misha denies that they're queerbaiting, then admits that he doesn't really know what the term means, but he doesn't think it's "accurate." Like a lot of things Misha says, it's a bit confusing, but there were several fans who were not happy at all with what he said there.)