Yesterday I reported this same bug (didn’t find this topic). It seems dependent on the the Legacy menu navigation, and it was already present the latest versions of 2.8.
The Dismiss All button workaround doesn’t seem work if that’s the only notification left, as the button is disabled in that case. Perhaps it works if there are more notifications — but then the person may be dismissing things that may be relevant.
As is, users will just get confused and/or frustrated. The few that complain may be told to use the button but that will only work in some cases. Shouldn’t this be moved to bug perhaps?