Found this explanation on Twitter. It appears that Ben actually deflected what was a shot on goal and the rebound was redirected into the goal.
"Rebound off goal keeper to a player offside is offside. If a defender attempts to play ball but missed header or wiffs a clearing pass and ball goes to offside player then it’s not offside under new college rule. Good call since goal was deflected by goal keeper to offside player. Go Zips!"