Okay, Pitt didn’t exactly set things ablaze with the 2015 signing class in national perception. Even before the coaching change this was going to be a small and not considered stellar recruiting class. Size matters in the calculations of class rankings. It is just a question of by how much.
Why does size matter? Because the bigger the class size, the bigger the impact on the team. Even if the class isn’t loaded with 4 and 5-star talent. The more players, the more likely — just based on quantity — there will be players that matter.
As each recruiting site weighs size differently, the impact is more noticeable. And obviously disagreements in the value of individual recruits.