I agree with your description but not sure about the precise mechanism. A razor blade will cut through all the materials best, so I think there must be a practical reason why sometimes serrated is preferred. In wood it is to clear a gap so the saw doesnt stick. This might be important in soem foods
I suspect that a serrated edge has the edge over an average semi-blunt knife due to its tearing action. Thinking about it now, a knife that is flat along its edge exerts little pressure as the force is distributed along a long surface whereas a serration exerts more force on its individual points allowing it to enter the material.