I would think that too if I spent all the big bucks on pneumatic equipment. You have a void in the soil (aerated) with your equipment but you have compressed the soil even more than it was around the perimeter of your blast. The auger removes the soil without compressing the perimeter of the excavation and then you can replace it with improved soil and other matter to retain the hole so roots can penetrate more easily than in your scenario.
Not sure that you don't have that backwards...
The drill still will make a shear compression on the walls of the hole. On the otherhand, have you ever stood near and Airknife/Airspade when it is plunged into the ground? It will lift you up several inches even if you are 3-4 feet away. So MAYBE (but I don't think so) it will compact some soil 6-8 feet away from the hole. But obviously, you should be gridding the holes closer than that. Basically, the soil moves "up" instead of "out". If it moved out...then yes, off target compaction would be a HUGE problem.
Bottom line though, I don't think added compaction is a reality (certainly not to the point it is a problem) with either technique. I do think the air is a little better because it actually fractures compacted soil between each hole in addition to just within the hole.
I am not sure I am convinced that the drill causes enough root damage to be considered problematic (as suggested by Rolla). Nor am I completely convinced that it decompacts enough soil to solve that problem. It certainly helps air and water penetration, and when you fertilize into the holes it gets that to the roots a little quicker...just not sold on the decompaction.