Trying to speak for Hitech's reasons does not work.
I can surmise though about GVDAR and it implementation. After building 4 terrains, the first three I was not as prepared as I thought to create venues for GV's to have more fun than the tree infested heckholes our AH2 converted terrains became with the new Speedtree vegetation. Hitech mentioned he had always had a GVDAR in mind but had not implemented it. I'm surmising he was not prepared either for how badly the new trees impacted GV's finding each other while getting entangled too easily in. Nor how well the new trees and bushes made it for a GV to become permanently invisible without customers wasting their play time hunting down a single GV. AHfilm became the gamey answer and still is.
The amount I opened up the trees with FjordMA to bring AH3 GV combat back to what was remembered in AH2 entailed a reduction of almost 80% of trees in a square mile. At least on that terrain getting stuck in a tree is something a player has to work at on purpose. And this only took me 3 terrains to acheive doing gradually more reduction in tree density to understand.
So the current GVDAR may well be in place becasue of the trees and all the problems related to them. Still, now with 3 years of experience by the community, I think defining a trigger radius from the field and a separate map identifier pops up while the GV is inside of that trigger radius is more than enough to help GVers and flyers know to sally forth. The red blocks with time and experience give away the GV's location.