It remains all superstition to me, one of the many superstitions surrounding gambling. If a madman can give correct predictions for a game, why has no shaman or prophet been able to give correct score predictions for several games?
Most times the people who tell this kind of story always claim to have heard it from another person; it is rarely a firsthand experience.
I don't take it as being superstition, probably I would say they are chances of lucks because such situations occur once awhile and have also witnessed the one of a drunk telling people about a sure predictions odds for a game and everyone that played it as said was amazed by the outcome, so in the aspect of the insane person I think it has 50/50 chances of becoming a reality.