This is just a way for whoever created the course to use semantics to emphasize a point. But the problem is, the person is wrong. Leadership can be used as a noun. Even the dictionary says Leadership is the plural form of Leader. The example the dictionary I used was "A change in leadership had the desired outcome."

I suspect the author of the training just wanted to emphasize the action meaning in leadership, and not this was a great sounding way to grab peoples attention.