I don't know if I'd call it a tree or not, but I pair Villages and terminals together and consider each pair to have costed me +0 Actions.
I think when I play with Crossroads I give the Crossroads a holding capacity of 2. So I guess I can see how that's a tree.
But like, if you are playing a Village and "treeing" two villages off of it and then Smithy's off of the lower level bridges I don't think you are making your board state easier to interpret (With KC and TR you might be haven't played with those as much)