Is this is a supported feature?
The above page doesn't mention it but why would you place rocks around a level which you could walk through? I've managed to get collisions with trees working by using a prefab with a Capsule Collider but having no luck with the same method for details...?
Anyone got a solution?
I guess No, cause the "detail mesh" is just to detail your terrain, like flowers and anothers small objects. If it uses colliders to details then the performance get down.
I guess you need to do the same as the trees, create a prefab with colliders and use the "Place trees" tool.