It is terminology , when I was overseeding lawns I was using a slit seeder that seeded right on the existing lawn, When I was renovating a lawn I would kill it with roundup and then overseed it, The purpose of either operation was that the grade and soil did not need changing, it was to eliminate the plowing , discing, grading or whatever else , just get the seed in. It sould be the same for whatever seed you are going to plant, any seed , any style of planting , the seed still needs to make contact with the soil, not sitting on a bed of grass mulch...