If I remember correctly, trees in Civ5 are not 3D objects, but 2D sprites. So they have many details with low graphics load, but no advanced 3D features like camera rotations will work with them.
Yes must be. I remember downloading a mod for civ v that replicates the camera rotation from civ iv, which I missed. When I rotated, everything looks terrible. Even some textures like trees became flat cardboards. Even the cities look off. That would explain why they got rid of camera rotation in v.