Under- and over-weight training has been proven to work.

Have seen it work in lifting, running/sprinting.

The use of weighted baseballs has been controversial but it works.

I have also tried it in the past for disc golf and it worked for me. Gained about 50' of distance one summer, threw my longest forehand throws ever.

Consistent, hard work applied to a suboptimal program more often leads to better results than inconsistent, lazy effort applied to a more optimal program.

But consistent, hard work applied to a more optimal program more often yields better results than either of those.

What's the best program? The one you believe in and stick with.

Yeah, we use to use under and overweight baseball's from time to time in baseball. We saw some good results.

The only studies I found showed over AND under weight baseball training to have no measurable effect. Do you have a source for this?

One could certainly spin. The 100 yr old dude is basically spinning.

But normal throwers that you show videos of are not spinning about an axis. There are pivot pints and leverage, but it’s not a spinning motion as such.

The goal of the throwing motion is to convert momentum to a force and linearly accelerate the disc.

The hip rotation is caused by follow through, not lead.

Here's a start:

Effects of General, Special, and Specific Resistance Training on Throwing Velocity in Baseball: A Brief Review (DeRenne et al, 2001)
Effects of Baseball Weighted Implement Training: A Brief Review (DeRenne et al, 2009)
Increasing Throwing Velocity (DeRenne, 1985)
Effects of Under-and Over-Weighted Implement Training and Pitching Velocity (1994)

I disagree. The backhand throw is all about rotating the body. The main distance in a backhand throw comes from a quick powerful rotation of the torso. The hip rotation leads the rotation of the torso and shoulders. There are guys out there who can bomb discs with the slowest x step on the planet. They aren't converting momentum into lateral shift to get distance. They are converting the rotational force of the hips, torso and shoulders to propel the disc. Adding more speed in the run-up is only slightly beneficial to distance.

I think the 360 throw is adding a ton more rotational velocity as well. Guess what, when performed properly it goes further. Also since we turn the shoulders as far back as we can in the backswing that is rotational as well. I would say it's both rational and linear. To what percent will vary by the throw and person.

I guess you could try throwing with no rotation but you won't throw it anywhere (like a putt).

You understand neither physics nor kinesiology.

Maybe you should post a video of your throw and we can compare it to a professional player. If you are against all odds on the right path as you say, your form should look very similiar if not identical ?