So, if it were true as the author says that "24-monthers" never develop the next level skills in the company, would it not also be true that the people who did

So, if it were true as the author says that "24-monthers" never develop the next level skills in the company, would it not also be true that the people who did in fact stay longer would have also become managers who didn't hemorrhage staff every 18-24 months?