Turns out that the branches and leaves of the large hossin trees do not have a hitbox, while the trunks do. But is it a feature, or just unfinished? I would like to think that it will be like this, it is a good way to limit sniper and general camper up in the things, and it also helps pilots. If so however I can see it being possible for players to hide inside these hollow textures.
I hope it's a feature, it's nice visual cover that makes planes harder to see while still being able to be shot down, plus it's nice to not be crashing into them every 5 seconds.