No cleanup required is relative.

With a Mafell mortiser the bottom of the mortice isn't flat, if you've engineered your timbers to allow for over boring then there is no cleanup on the bottom. The chamfer on the tennon helps keep the required overbore to a minimum.

I believe the Makita plunges to three slightly different depths with each set of the head so a similiar situation exists, is this correct?

The Mafell will cut right to the critical lines on the ends of the mortice nice and smooth. The sides of the mortice have some chain texture that cleans off in about 20 seconds/side.