He has enough arm power and speed to have some snap but even in half hitting domain he is lacking in the rest of the body. DG throw ain't weight lifting or smashing objects with a super heavy sledge hammer. The muscles will be taxed a lot in the last few inches of a toss when you get a good disc pivot and grip pinch the hell out of the disc but before that you should be pretty loose. The places where you do exert yourself are left leg push starting the throw, the right leg stiffening to brace for a while in after the plant to transfer the momentum to start the twist of the hips, hips twisting actively and wrestling the wrist down after the elbow starts to straighten out. Stiffness anywhere else should be hard enough to maintain posture and the angles of the disc and otherwise as loose as possible. That means that he is stiffer in more places than need be and all the time. Big time. It's not like he is trying to lift a new record in weights like he uses his muscles now. It's more like fuck what was that!!!??? turning around for your life when an oncoming train honks three feet from you and you instinctively turn as fast as possible to see what the threat is. That is instinctive. If you sneak up on him and crash two cymbals together behind him or ask him to remember how fast the twitch motion of being scared to hell for your life or removing the arm from something hot is those are the feelings in the muscles one needs to have much of the time in the throw. The muscles feel like they tense up only in the outer layers. Not through and through like in a weight lift. I imagine throwing a shot put ball or hammer throw hammer is so stressful that in those the muscles are taxed through and through.
In disc golf the discs are so light that the arms have enough power to move faster and force is mass times acceleration. Kinetic energy is half the mass multiplied with the velocity squared. In a real throw the longest flights come from as much velocity as possible combined with as much acceleration as possible without compromising speed at all. I can't say for sure if you need to sacrifice some acceleration to gain more speed vs the max acceleration you can muster. It probably depends on the thrower too. People have different speeds, strength and ratio of fast cells vs the fastest muscle cells. The automated twitch of the reflex of pulling away from a hot thing is faster than you can achieve consciously i think. One should strive for that kind of quickness to max out the acceleration. Try catching flies or gnats with stiff arm muscles. Then with loose muscles. Which one do you think will catch them? That illustrates the meaning and need of muscle control and not being stiff all over.
Flat shots need running on the center line of the tee and planting each step on the center line. Anhyzer needs running from rear right to front left with the plant step hitting the ground to the left of the line you're running on. Hyzer is the mirror of that.