Maybe I just don't get it, but the tooltips on Dredge/Prune and Unearth/Leaf Turn are identical, are they not? Same cost, same effect, kept apart by some 40 levels.

What's the point here? What am I missing?

I can -almost- understand Dredge II and Prune II, since they give a different bonus to the II's of the originals, but ... what is up with these two abilities?