Spinning doesn't mean throwing any farther. The records for each are only 2 inches different. Gliding is more consistent and is a seen more at the higher levels in Europe. Spinning gives a longer time to accelerate the shot but provides more places to make mistakes. Greater risk vs greater reward. There are also significant limitations with the spin once you obtain a certain height. Torque limitations vs overall room availability in the ring. World class spinners (generally American) average about 6'4", gliders about 6'8".
Based on the discus film I watched spinning would not help him throw further. He has flexibility issues that will take several years to overcome but it would be good for injury prevention down the road.
