Please correct my opinions if wrong.
you get reduced drift because the vast majority of droplets are similarly sized regardless of the wind speed -- for example.
That is fairly true. Most drift reduction technologies (Air induction, closed chamber) will reign in the droplet spectrum to cut down a lot of the 'too small' and the 'too big' droplets.
Think of it this way:
Conventional Flat Fan Tip: Droplet sizes of 5-1000 microns (numbers are just a made up range)
That is a big range.
With air induction (ABJ) or closed chamber (Wilger), you are introducing turbulence as well as a pressure drop into the tip. The pressure drop creates bigger droplets, and the turbulence both consolidates the small droplets within the chamber (Think of them hitting eachother) and the 'too large' droplets are split up with the turbulence to make more USEFUL droplets.
So, effectively this could change the droplet size range to something more around the lines of 200-800 microns. Closed chamber (Wilger) has differing ways to adjust that droplet size range a little more (by adjusting pre-orifice sizes as well as the actually stainless tip orifice size), but its the same idea whether it changes the range to 150-700 microns or 300-900 microns.
That's essentially the difference between the two types of tips. (conventional vs. Drift-reduction)
So, when they say the droplets are more around the same size, it is more that the science is adjusting the droplets to be more meaningful to the actual applications. All of this 'science' is happening before the spray leaves the tip, so wind doesn't really have any effect on the droplets when they are formed.
Whether the wind shear cuts down droplets on their path to the crop is another story though.