You'll hear different opinions. Lots of muscles are involved in a reciprocal motion so people get understandably confused. Some of them are stabilizers, some of them are workhorses. There's a bit of real variability among far throwers IMHO.
Learn to copy Gibson's little drill move there. Exactly.
Then do this one. Exactly. Notice that the disc is still moving slightly back away as his weight is shifting forward. Doesn't need to be big.
Notice what, where, and when the arm sequence wants to activate in that context.
Consider why he doesn't every look like he has an elbow forced forward to make a "pocket" in that drill move, which is why Sidewinder made his "power pocket explained" video.
Exaggerate little bits at a time one way or another. Notice what changes and what does and does not keep you in balance. Notice when the arm wants to compensate for being too ahead or behind of the weight shift and rest of the body moving in posture. Notice the lateral part of the weight shift and
curved path of the disc and arm out of the backswing peak that is caused by that shift and how his posture guides his arm. Learn to feel how all of it happening right is related to any of it happening right. One big move.
Look, do, and feel what is happening here. It's right there for the taking. Do it, then watch the arm. Watch the feet. Watch the body. Then do it again and again (and again and again):
Also why I still prefer to conceptualize all arm questions within this:
Can you try to throw other ways? Sure, people do lots of things. YMMV. I have tried every other idea on the market I'm aware of & some of them have their place IMHO, but none of them worked as well or looked as good as everything else I think I've learned about form as the above. Everything else ends up being too forced for me. I like throwing farther with momentum and little to no effort. My arm is involved, but my answer is the above. Again, YMMV.