There is a dependency to the TreeSelection class in the the TreeControl class, it is caused by the method "Add Items" which has an object reference to the TreeSelection class (instead of the TreeControl class). The method "Add Items to End" in the TreeControl class is also stored in the wrong folder (it's currently in the TreeSelection class folder).
You're right the "Add Items to End" method was in the wrong folder. I have fixed it for the next release.
As for the "Add Items" method, the TreeSelection class specializes the "Add Items" method through inheritance from the TreeControl class. This is so it can add the symbol for the checkbox as well. It looks to me to be in the right folder.
However, that leads into a discussion...
When I wrapped all of the built-in VI Server methods, I made them overrideable. I think this is helpful because you can then extend or change the behavior of the original method. I did this with all of the built-in VI Server properties as well.
There is a problem with the method "Add Items", but maybe it is supposed to be part of the TreeSelection class (but I guess there should be a method "Add Items" in the TreeControl class as well)?
As it is now, the class TreeDirectory, which inherits TreeControl, can't call this method (which should be possible).
Okay, you are right. I am seeing something weird there. I was confused because the Add Item.vi was correct but the Add Items.vi (with plural items) is wrong.
The class input/output is TreeSelection when it should be TreeControl. It looks like I never finished the VI properly because the other inputs and outputs and errors weren't connected to the connector pane. I will fix this for the next release.
I am currently finishing updates to the documentation and then all fixes to this point will be submitted to the Tools network.
FYI. Here is the fixed VI (also attached).