In which case -
1. If the sites are capable of doing the same evaluation and don't see it in Neal - then he is only a good but not great player and can't be given a high ranking.
2. If the coaches can see it and the sites can't or don't then he could be a great player but won't get it since they don't see it and he won't be given a high ranking.
Is this reasoning right?
Both of those sound reasonable.
Its important to note that even good coaches...guys that get paid lots of money to do nothing more than evaluate prospects...often disagree over just how good a player can be.
For me, I can understand why Neal is a 5.7 3-star. I'm not outraged. It is a safe rating; right on that bubble between a solid good and very good prospect. Factors that Neal cannot change are what is keeping his rating from going higher; he can't help that he is not tall, or that he can't run fast, or that he can't get bigger because there is no more room to add weight to his frame.
Still, what impresses coaches that watch him are just how sound he is: how he always keeps containment through outstanding positioning and vision; how he keeps from being wired to the blocker by using his hands and arms; how strong he looks; how good his instincts are; how he is a superior tackler.
LSU and other schools like Ohio State offer many 3-stars every year. Many of them become good players, some become great players, and some become supportive depth. I think Neal does enough things well to make me happy that he is in this class but I also understand how he is not viewed as a "can't miss" prospect.