Ah well... I think we can come across equally strange things in both the worlds, just that they seem more "acceptable" in fiction since we give it that leeway - call it suspension of disbelief. We might agree to a few things with a pinch of salt mainly because it's a story after all. In real life, acceptance is not so easily found. There are moral judgments, there are financial considerations, and a thousand other social obligations that make the same kind of 'fact' stranger.We might as well find way too strange things in fiction, but real life occurrences will always be more unpalatable. I think that's what lends credibility to this phrase today.