Is this a bug with private forums

[mrgtb]

If you add a private staff forum, but set permission so anybody can view the forum, but only staff read it. And that private forum is a SUB FORUM of another one that is fully public for members to read whats on it. Thread title get displayed on the main parent forum of the private one, if you add new topics on the private forum and it was last one added (so it's seen on parent forum as well). But when viewing the private forum the thread title is removed, as is should be. But not on parent forum, it shows thread title to guests even though guests and members cannot read what is posted on that private forum, only staff can like admin and mod

What I mean, the parent forum of the private one is not respecting permission - showing thread title for the topic added last on the sub forum to it, but a sub forum that only allows staff to read new topics (not guests or members). But still shows the thread title from that sub board (while the sub board hides it)