Demonstration Video: https://youtu.be/eQ_YiWhfJWY
It appears that projector priority seems to be using inverse the light radius to calculate shadow priority.
  1. Make 3 projector lights equidistant from each other pointing towards a centerpoint (for ease of seeing the shadows)
  2. Adjust the radius of the light furthest from your view larger and smaller and observe
  3. Adjust the radius of the light closest to your view larger and smaller and observe.