Not necessarily true, I got flats with them from Goathead thorns. In fact the only tire I found that a Goathead could not penetrate was the Specialized Armadillo All Condition Pro, I didn't try the Schwalbe Marathon Plus HS 440, those Schwalbe tires are suppose to be flat-less according to the manufacture, I no longer live in Goathead country so I don't need that kind of flat resistant tire, but I would wager a bet that the Schwalbe tire is probably better than the Specialized, and certainly better than anything Conti has or any other manufacture has currently on the market.