Here is some info on Beam Divergence. It looks older but explains why certian beam divergences may be chosen. Looks like manufactures have to weigh the pros and cons to their choices.
I read in one of my college physics books that the size of the beam and the sensor can play a big role on how much divergence can occur and still get longer range reliability. This was information on much larger rangefinders though including aviation technologies. Not sure how much could be applied to handheld optics.
I cannot wait till we get some reviews on this bino. I really need a new rangefinder and the larger field of view would be great + less gear to haul around and much faster calcs for long range shots.