Exactly. Not only aren't people random, they're predictable based on history[0]. Each person could only be asked for one number and they shouldn't even wait perceptibly different lengths of time to be asked.
I've tried this a few times (refreshing the page in between). After a hundred or so strokes the computer is consistently less than 50%, usually ~45%. Suggesting my brain has somehow spontaneously worked out whatever algorithm it's using to guess. I don't think I'm random but there's something too simplistic about the method on this page.