The typical use of the split line is for the projection of a sketch onto a surface/face to split the face up for various reasons. Draft lines, hold lines, forming tools, simulation setups and the like. The one other one (of the 3 types) that you might not know is the intersection as shown here is the intersection of 2 surfaces. It could very well be bodies, faces, or planes.
In this case what really have here is a projected curve onto the face with out the curve part sucking up resources. Plus the fact that we do not have to do another feature to split the face or whatever our next move may be such as an edge treatment with a swept cut or what have you. In my case I needed flexibility to control the height of the surfaces quickly to make the asthetics of the part eye pleasing and easily updated to show various edge treatments for a final outcome.
Just another tool in the arsenal for you to experiment with…