The site asks you to pick a random number, not mentioning anything about trying to achieve a specific distribution.
EDIT: Downvotes and no comments, nice. You guys seem to be misunderstanding something. If asked to picked any number ("random") between 1 and 10, to suggest that the outcome is "wrong" because the distribution isn't uniform doesn't make any sense at all. It would be a completely different experiment if we were asked to pick a number between 1 and 10 such that the outcome after x number of independent trials has a uniform (or gaussian/exponential/etc) distribution. This seems to be what some people are assuming.