Well it is related to the scenery because all the parking shows up as RAMP, either GA or cargo whereas no other airports do that which is probably causing a problem with AI.
No, the only reason for that, is to get rid of the default ground vehicles and default ground markings, to be replaced by the custom ones.
The only effect on AI traffic would be that, IF AI models are missing the airline designation, they will start populating the airport with a different distribution, but they will show anyway.
If, instead, the AI models ARE correctly flagged with their airline code, they will park at the correct place.
We tested the scenery with default MS traffic, WorldOfAI, AiArdwark, EvolveAI, FSPainter and PAI models, and they all work just fine so, if you don't see any traffic, it's obviously nothing related to the scenery. There are also many screenshots from other users with AI traffic in this board so.