Couldn't it be explained that some students memorized things better or more systematically? You could argue everyone studies the same thing in school too but there's a bell curve based on how many passes someone wants to go over material or how gifted they are or if they found their most effective study method.
People may know of FA, UWORLD, zanki, etc but not everyone dedicates their full effort into it. From what I've read on some breakdowns, some people said they studied those resources but made 1 or 2 passes, others said they had all of FA memorized through bros or flashcards, and some just referenced it. At the same time there are people who have gotten great scores through sheer effort (the most recent post was the person who did like 150k zanki cards and had a strong score before even dedicated. Not everyone puts in that effort or time.