Turning has never been a good practice , best never to get to the point it needs turning . I have only turned a disk once ,warped after a few weeks use , never again . Use them for about 2, maybe 4 sets of pads and off they go . Not worth it , what's the charge for turning a rotor ? New rotor is beween 20 and 80 for the better grade ,
well you are correct if the rotor is near minumum spec or is designed not to be turned
BUT
other rotors have enough meat on them to allow for a couple turns with no issues of warping... now if you do now brakes in your breaks you can have lots of issues no matter what kind of pad or rotors...