I think there are a few reasons why Joly was ranked so low. He was an under the radar player. His junior year, 2020, the schedule was pushed off into a shortened spring season due to COVID and his stats were somewhat modest with 21 catches for 351 yards and 4 TDs. He blew up his senior year where he had 67 catches for 1033 yards and 10 TDs. Plus, he had 37 carries for 362 yards and 3 TDs. And, he was committed to Delaware so that didn't help his visibility. Throw in that he was listed as 6'3" 190 lbs on 247 and 6'4" 215 lbs on rivals. So I agree with Silver, he was a tweener probably not fast enough to be ranked highly as a WR and not big enough to be rated highly as a TE.
So you had a tweener late bloomer who missed a full junior year who blew up his senior year. Most FBS spots are already gone by then and UConn had a spot. Remember, back in the day, Edsall liked to see senior year results as you can find the late bloomers who have been overlooked.