I am not a professional mechanic, I am a machinist though.
When diagnosing an electrical fault it is important that your reference point you are measuring to is good, i.e. you need a good ground or your measurements won't be accurate. Likewise when taking physical measurements your reference point is equally important. You can't reference the rotor surface to know if the disc is squarely mounted as the rotors surface is most likely warped. The only place you can reference is the rotors hub where you are mounting (though it looks like the adapter on the brake lathe used takes up most of the face of the hub.) A dial indicator indicating on the face of the hub will let you know if the rotor is mounted squarely.
Indicating against the rotor surface, with a dial indicator or a wrench (as shown in the video) only give you an idea of how warped the rotor's disc is. If it is very warped you are not likely to be able to square it back up to the rotor's hub without cutting off too much material. Also, if it is that warped the rotor will have likely been permanently damaged by heat.
the minimum cut thickness is stamped into every rotor if by a micrometer the thinest spot is minimum or less replace the rotors if you have warped rotors beyond ten thousands replace them as well other wise USE COMMON SENSE // DONT CHANGE PARTS UNLES U MUST DO SO
A lot of brake vibrations are down to deposits baked into the disc surface rather than actual warping, one thing that can cause disc warping or surface deposits is when stationary holding the vehicle on the foot brake when the brakes are very hot after hard use.
European Fords with strut suspension used to be particularly prone to front brake vibrations, the OEM brake manufacturer Girling sold special abrasive coated brake pads that de-glazed the surface and was very effective as a cure.
Brake disc wear and corrosion is a much bigger problem than it was years ago as modern metalized friction materials have replaced asbestos based brake pad.
This is also the reason why brake dust now causes so much damaged to wheels.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
