I think, there's still something wrong with tree and the expand functionality, maybe, lnh, that's what irritated you a bit.
For network drives e.g.: Open a a location within your lan (UNC) and toggle the tree to open, the unc-folder will be expanded in the tree, even though the settings are set to "populate contents for local devices only". Now switch from source to dest an back and that network location folder in the tree will be collapsed. Toggling the tree expands it again, which I think is odd.
On the other hand: I have also selected "Expand selected branch" and the currently selected local folder I have opened in source or dest does not expand, which I find odd as well. (Look here: Tree "expand selected branch" not applied on focus change Tree-View item out of view) which is aehm.. I mean I have no explanation! o)