Exclude subgroups in smart rule

Hi all, I’m wondering if this is a bug or just something I misunderstand:

I have a smart rule that looks for documents in the general Inbox with a certain tag and moves them into a group within the Inbox.

Obviously, once they are in there, the rule doesn’t have to see them any more. Therefore, I checked the box ‘exclude subgroups’ in the smart group editing panel.

However, the smart rule still sees all the documents, on the top level and in the folder.
Thinking a group on the top level is maybe not a real subgroup, I put the destination group inside another group. But that doesn’t change anything.

Do I misunderstand what the ‘exclude subgroups’ does?

image

When using Exclude subgroups while targeting the parent group, I am not seeing any of the bookmarks in the Bookmarks group shown here.

Screen captures could be helpful.