If "the house" was not making money, even the "professional sports bettors" would be out of the business. Of course there are some winners, even some relatively consistent winners. Also of course, these are the ones that get advertised.This is just basic game theory, ever heard? Question wasn't about house's edge, gambling etc.
John can guess right 42,86% of time (3 of 7) in average.
Out of the record, there are professional sport bettors who make their living by sports betting, so no need to act "smart".