Yes, would be more realistic.
But ... probably hard to implement?! So far I believe only complete meshes can be defined as solid or not. Might mean to split the whole tree into a solid branch mesh and a virtual leaves mesh?
If the game's engine works like the Unity engine, then yeah, you can only make 1 mesh either solid or not. However, you can split the meshes of the two things and make it work fine, either that or just put a collider around the tree manually in the desired 3D program that only covers the center of the tree. There's quite a few ways that it can be done, and I only named two (manual collider and splitting the mesh).
BTW, when I say collider, I mean a collision box. The collision box can be any shape as long as it isn't concave.