In current CNC production, the finish is so fine and the fit so close to perfection, that even the honing process is usually redundant..
CNC machines are not a replacement for grinding/lapping machines. See at these photo of pistons photographed under microscope
Also they are centerless grunded or lapped. I searched after the tool marks by CNC lathe and there are the tool marks who are not complete removed by centerless grinding machine in piston from unused OS 21 SE-M and there are lapping marks in piston from Thunder Tiger 07 GP.
Current production pistons are barrel ground to their final size and sleeves are honed to their final size.
See at the photo, the pic tell more. Also not barrel as we allways thinked before. Sure not all engines has allways been barrel grunded piston in ABC/ABN engines as 2 difference engine manufacture are making the cylindrical grounded pistons are showed there i took measure of piston. The last pic of crankcase are showing the engine are unused.
This process is indeed 'lapping' and I admit that I did not know there are manufacturers which employ such a preliminary process.
It is important to remove tool marks first before chrome/nickel are applied. It is to preventing top of "mountains" after lathe tool are grunded/lapped off and there will be visible brass/aluminium spots. After the chrome/nickel are applied, then lap again to make true bore (there are not same thickness overall in chrome/nickel layer) and smooth surface + a lot of oil pockets.