What it always looked like to me when squaddies and I had disparities between what we were seeing on bardar is for some reason I was not getting the bar dar because I was too far away. Once I got my plane close enough (it felt like it might've been 10k, which if memory serves is dot distance or when things actually start to exist on my client) suddenly my bardar would sync up and all would be good.
Yet at other times such as upon login, you appear to get bar dar from all around the map regardless of proximity.
If it's working as intended and somehow supposed to be a "fog of war" thing personally I think that's not a good way to do it. It should show what's in the air that meets the conditions that should result in bar dar map wide.
Wiley.