I have heard some dealer excuses in my time but that beats many of them............ it is rubbish to imply the wheels are at fault.
For rotors to warp you are talking about excessive heat, have you ever smelt your rotors being hot, it is a very distinctive odour, if I drive with some gusto I definitely heat the brakes up.
One of the lessons I learned from my brake overhaul is that the rotors/discs have to be seated correctly before tightening the single screw, When you say all rotors does that also mean both front and rear, or just one but replaced in pairs?????
If your brakes were continually binding you would feel it when you drove the car......... I do think one issue could be with the hydraulics which manage the brakes the anti skid and DSC etc.
As far as their evidence is concerned get them to show and explain their rational ??
Always said I would go back to a 6 series