Disappearing Parts and Folders in Edit Window

Can someone explain the thinking behind the way in which folders/parts are edited in the edit window when they’re all selected together?

Here’s the scenario I’m working with. I have 15 midi parts. 10 are in a folder called “plucked” the other five are piano,bdrum, bass,pad and vibes. If I select all the parts (including the folder) and go to the edit window. The moment I move midi note, the things in the folder disappear from the edit window.

If, however, I expand the folder and select only the midi parts, this does not happen and I can edit to my heart’s content.

also, If I select two folders this behavior doesn’t occur.

Is this a feature or a bug?