It's kind of half each. This sounded familiar and a short search produced this and this - an article on ORBX' own forums is the fourth link on the first page if you search for "traffic global" "orbx" "egnx" in Google.
Those airports seem to have a few problems. First - apparently - much of the parking is only for prop planes which restricts things a lot. Second, many parking slots are on taxiways. TG removes parking that straddles a taxiway because many airports have parking spots - which are also user start locations - at the hold-short points. If something parked here it would block the entire airport. It's OK with taxiways that go directly to parking if they're dead ends, even though that's explicitly not what you're supposed to do according to the X-Plane design docs. However, the taxiways for these airports go through the center of the parking spot and are also loops. So, they're seen as valid taxiways and the parking is deleted.
To be fair these things are often overlooked, they really only matter for full traffic providers that use the X-Plane data "as is", and most people have X-Plane AI traffic disabled.
The good news is that ORBX are aware of it and if you contact their support they may have an updated airport. For future reference, I don't know if you contacted Just Flight support but I don't recall this one being passed on and the forums are really for user-to-user advice, not support ;) Might have saved you some time searching.
