FWIW using the Add-Ons tab's search for "tree style tabs" gives 9 results, none of which include this add-on.

But when I click "269 more results", then Tree Style Tab is the first result on that addons.mozilla.org page.

(This isn't the first time I've found add-on search to be a bit wonky. Maybe "everyone" knows to ignore the first results (?), but I don't search for and install add-ons frequently enough to have learned that, quite yet.)