Pure speculation - a one second burst of 20mm would be about 100 rounds, maybe a balloon wouldn't be a substantial enough target to detonate the rounds, and maybe they didn't want 100 or so live explosive/incendiary rounds coming down on friendly territory.
Apparently the balloons did have enough return to detonate the Sidewinder's proximity fuse.
Or maybe default is "missiles first"?
Again - pure speculation.
We think the same, with the military gps ability there is no reason for them to not know where the 20mm bullets will end up on the ground...mb
