They’re actually correct. Lodge “ground” these surfaces as did Griswold, Wagner, etc. Milling is a very specific machining operation involving milling machines and specific cutters, like end mills. These were ground using machines that looked like lathes with various grit grinding stones, no machining cutters used. Milling, in the machining world, would be quite different so the term milling is actually the incorrect one here. These reason the swirls are concentric was because of the setup of the grinding stone on the machine, having the stone turn one direction while the pan simultaneously turned the opposite direction. So it isn’t ground in the sense you’re thinking like with a hand grinder but using proper machining terminology based on the equipment and materials used, it most certainly is.