Maybe I don't understand the question. The foot on the side and the addition to the base plate serve the same purpose, just that the addition is more stable. Both support the off-rail side of the router to keep it level with the the side on the rail. As far as depth of cut is concerned, foot and addition are the same.
Just reviving this old thread in order to ask the question -- is there an engineering reason why the depth stop turret on Festool routers is spring loaded, introducing the potential for overshooting the depth if you don't press down hard enough to engage the spring? Is it just to make it easier to turn and lock the turret into place?