This question, touched in forum #13651, is still an issue.
It just does not work the way it is. People do not know about the intended use of leaf and use it instead of leaves.
The general tag should be either "leaf" (sometimes singular does make sense: post #608273, post #603384, post #593818, post #587485, etc.) or "leaves", with an implication to the other one.
Instead of current leaf there should be something like "leaf_(studio)".
I suggest doing this soon. As the time passes, it will become more and more difficult to separate the "real" leaf images from the growing unsorted mass.
Updated by wanchan