I have little doubt that this is the right move. Think about it.
Our teams two best linebackers are Willie Harvey (6' 225) and Reggan Northrup (6'1 2015) (those are from last years rosters, they're likely bigger now). Both of them play WLB.
The SAM LB is seldom used in this defense and will be played by two young guys (McMillen and Spears).
The MLB spot basically only had a RS Fr and walk-ons on the depth chart, since Brian Mills (likely would have been a MLB contributor again in 2017) left the team.
Joel is not the best QB, would not be the best RB, and would be behind two VERY promising young TE and two great blockers at 'H-back'. Where else are you going to put him?
He's pound for pound one of the best athletes/football players on the team, why not try him at a position of need?
Great move that can only help you.