He has this completely wrong. The idea in pare-mutuel betting is not to pick the winner. The favorite usually wins, but the house cut makes betting the favorite a net lose. The goal is to find underpriced bets, where the collective estimate of the odds is far from the prediction systems's estimate.
Isn't this a misstatement in the other direction? Favourites can be underrated too.
They're probably not, or at least not enough for you to beat the house cut, but that's true of every bet -- they're all likely to be net losers unless you have special information, or a special way of using it.