Dealer has minimum rotor thickness specs?

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I took my car in for rear brakes today and when I read the invoice after coming home, it read:

"Inspected brake linings. Front pads at 10mm, rears at 2mm. Rotors at 10.3mm, min=10.4mm. Remove and replaced rear pads, rotors, and sensor."

I had the front replaced 2 months ago and did not have comments like this. BMW has been replacing my brakes for the past 20 years and have never had anything like this. They have always replaced rotors and pads together.

So is BMW instituting a min brake rotor thinkness at this time? I wonder if my rotor thickness was at 10.5mm or 10.6mm, would they have turned it and reuse it? Anyone know?