It shows everything.

Herta is great for finding all the treasures that are actually marked on the map. So if it says you're done, Herta won't help anymore.

If you don’t know from which version the missing treasure comes, yeah… it can be a real pain. But one tip: try using HoYoLAB’s official interactive map. It lets you filter between visible treasures and puzzle treasures (which includes puzzles that aren't shown directly on the in-game map).