Is the term not about getting so close to real that it's that the remaining shortfall makes us uncomfortable?

E.g. something "50% real" is so far off, we psychologically dismiss it as a cartoon, drawing, whatever. It's not trying to compete with real.

Something "98% real" freaks us out though. Surprised I have not yet seen this link:

http://blog.codinghorror.com/avoiding-the-uncanny-valley-of-...