Most scouting services never provide the complete picture for any of the FCS programs - Rivals included. They do not even show three of the commits in the list for UR, and provide zero visibility into most of the CAA or other FCS conferences. Scout, 247 and ESPN are all the same.
It is so subjective when they do rank these kids -look at the kids from VA (9 of them) on the Hero Sports list and then compare it to how Rivals ranked the VA kids. Only four of the top 45 players ranked by Rivals are going to FCS programs, and two of them are part of UR's 2017 class. The two others (Drew - Villanova and Mitchell - W&M) do show up on both lists, but what about the other 7 on this guy's Top 250?
This is one analyst from FL trying to assimilate all of this data - and incomplete data set to boot - so a truly difficult task to accurately complete.