This is the equivalent of closing all tabs, with the added bonus of having a list of what you just closed. I refuse to compromise on functionality because Chrome can't get its memory deal together.
It should be noted that Chrome has a built-in "Bookmark All Tabs" button which will bookmark all tabs in the window into a folder... This extension doesn't seem to add any functionality on top of that.
For instance, your workflow doesn't work for me because "bookmark" in my life pretty much means "lose this page in my junk drawer of pages that I'll probably never read again, but I might if I'm ever stranded on an island with nothing but my cached bookmarks."
So I have a completely different workflow that you'd probably find equally extraneous, but it works for me.