Yes; I totally agree the bottom line is that skimming or changing the disk rotors will likely remove the judder.
But I am still interested in the "academic" aspects of the causes and cures of disk brake judder. What appears to be the transfer of material on to pads causing brake pedal pulsations certainly is a common issue on our Australian made Fords (although sticking calliper slide pins is probably an even greater cause of brake judder on them). I wonder if it is a climate related issue (little snow in most parts) or perhaps in part at least it is because Australia has successfully banned the use of pads containing asbestos while the US ban attempted was unsuccessful (see https://www.epa.gov/asbestos/us-federal-bans-asbestos
etc.) and we a stuck with safer more synthetic material is our brake pads.
And cementite on rotors is apparently not usually visible to the naked eye. Google "cementite invisible" to get lots of references. But nonetheless I have to acknowledge a Google Scholar search on "brake judder" for me at least gave no definitive answer and no confirmation that pad material transfer was a common cause. Perhaps cementite is just a localised thickening of the rotor due to changes to the chemical composition of disk metal rather than transfer of pad material. As they say here: http://www.powerbrake.co.za/Articles.asp?ID=253
"When the temperature around these high spots reaches 650 – 700°C. the cast iron in that area will change structurally and transform into a material called Cementite. Cementite is far harder than the cast iron of the unaffected parts of the disc and will therefore wear considerably less as the disc wears down with use.”
One paper concluded (e.g. Interactive Effects of Thermal Deformation and Wear on Lateral Runout and Thickness Variation of Brake Disc Rotors
) that hot judder is caused by deformed rotors but almost most seem to agree all brake sourced judder is due to variations in disk thickness (DTV) and often attribute it to changes in the surface of composition of the metal of the disk rather than direct transfer of pad material. And this paper The role of raw material ingredients of brake linings on the formation of transfer film and friction characteristics
suggested that "the transfer film on the rotor surface reduced the amplitude of friction oscillation". Similarly, The Role of Transfer Layers on Friction Characteristics in the Sliding Interface between Friction Materials against Gray Iron Brake Disks | SpringerLink
had this outcome: "Results showed that the transfer layer formation was highly dependent on the relative amount of ingredients in the friction material and temperature. Among various ingredients, solid lubricants and iron powders increased the transfer layer thickness but no apparent correlation between transfer layer thickness and the coefficient of friction was found. Strong influence from individual ingredients was observed, dominating the friction characteristics during sliding. On the other hand, the thick transfer layers on the disk surface tended to reduce the friction material wear and the amplitude of the friction coefficient oscillation during sliding." If these two papers are correct often layering of pad material would actually reduce brake judder.
It seems I am not alone in being puzzled by the actual cause of brake judder. This paper noted "There are numerous publications available dealing with high frequency vibrations, such as brake squeal, including mathematical models for analysis and simulation. However, low frequency phenomena, such as brake judder and groan, have received much less attention. There is a growing interest from the automotive industry concerning brake judder. Even though few companies would admit that they have the problem, it is not unusual to meet people who have experienced the problem in their own passenger cars. Much of the knowledge concerning brake judder remains within the companies. Hence, very few people have the full picture." I guess it could be as suggested "an industry secret" or perhaps it’s just that nobody really knows.
One interesting finding was that relevant to the original post though was: " the causes for brake judder do not always relate to the brake system but also to other components" http://papers.sae.org/920554/