Tyler Cowen argues in a TED talk (~15 min) that stories pervade our mental lives. He thinks they are a major source of cognitive biases and, on the margin, we should be more suspicious of them - especially simple stories. Here's an interesting quote about the meta-level:
What story do you take away from Tyler Cowen? ...Another possibility is you might tell a story of rebirth. You might say, "I used to think too much in terms of stories, but then I heard Tyler Cowen, and now I think less in terms of stories". ...You could also tell a story of deep tragedy. "This guy Tyler Cowen came and he told us not to think in terms of stories, but all he could do was tell us stories about how other people think too much in terms of stories."
The number of possible scores is limited by the size of the board. The number of available moves is also on the order of magnitude of the size of the board. The birthday paradox says that there is very likely to be a collision. Even more so since the scores aren't evenly distributed.
It's somewhat harder to estimate how often the best move will be one of the ties. Equally matched good players tend to end up with single digit (delta-)scores, which greatly reduces the range, and I have no particular reason to expect optimal play to differ in that respect. But if I invoke that statistic, then I also have to reduce the domain to however many moves said players would be unsure between, which I don't know.
I don't think you can use the birthday paradox here - since the expected values of go moves are best treated as being surreal numbers:
http://en.wikipedia.org/wiki/Surreal_number
Surreal numbers were actually originally developed to handle go move values:
http://senseis.xmp.net/?Infinitesimals
http://senseis.xmp.net/?GoInfinitesimals