TYPO3 Core

I don't know if this is a bug or feature... but it's neither what I expected nor wanted. I give you a brief example of my situation:

Unter my page root I have two trees A and B. I created two BE groups and put A to the first group's db mounts and B to the other. I also created three users (like creator, reviewer, publisher) for each group. After that I added a new workspace and put the creaters, reviewers and publishers to the corresponding fields.

Everything's fine so far. I can log in with any of these users, just see the part of the page tree this user is responsible for and can edit my things.

Now, when both - groupA and groupB's creator - make changes to a page and trigger the workflow the odd thing happens. Each user sees both changes in the workspace view. It's like the db mount restriction in the groups don't affect the workspace view.

My question is: should it be like this? And if yes, is there a way to work around except creating a single workspace for A and B?

(issue imported from #M4264)