I believe it's not so much the light as it is the shadows from the light that effects them more. When using any light source movement discipline is a must. If you're shaking the light every shadow down range is shaking in their face and that is what spooks them. You can see this effect best when driving. Everything from a yote to a rabbit can't make up its mind where to run because the shadows are confusing them. If you talk to old timers, everyone of them used a dimmer switch on their spot light. And like scalebuster said, a lot of guys now just use the halo until target is set up. The reason is, the lower the light, the softer the shadows. While the yote is approaching, the soft shadows won't spook as easily.
Now with my ND3, I think it actually is the light source. I've noticed that when any animal is on a head on approach and I light them up, they will turn or close their eyes. But on a broadside approach they act as if it is not there. The ND brand lights are lasers, and emit a total different type of light.