Safari tooltip bug

I was reading a post by Craig Turner about a tiny but neat feature of Safari, and I was checking out the tabs in a window I had open right now. Safari certainly does seem to be picking words of interest for the tab titles, but in the process of investigating this, I discovered a tiny but amusing bug of Safari: it gets some of the tooltips just plain wrong.

There certainly is a Gmail tab open, but it's not the tab under the pointer.

Safari