New cars used to use a thin metal spring washer that slipped over a lug bolt to hold the brake drums on while the chassis went down the assembly line. Kept them from slipping off and landing on someone’s toe (or head). When they switched to rotors, they switched to a screw that indexes the rotor so that it goes on in the same orientation that it came off. I am not sure that is all that important since I don’t think they spin balance the rotors in place on the car.
As for lug nut tension, that is all about heat transfer. A lot of heat transfers from the rotor to the hub and to the wheel. Heat transfers more effectively around a tighter lug nut. Several thousand cycles of uneven heating and cooling tend to warp the rotor.
As has been pointed out here before, a lot of tire shops claim to use torque wrenches to tighten the lug nuts, when in fact, the use the torque wrench only to double-check that they have tightened all the lugs. By the time they pick up the torque wrench, they have already over-tightened and unevenly-tightened all the lugs with their impact wrench. That is why I carry loose wheels to the tire store and mount my wheels myself.