OK, well answer me this then. If a new car didn’t have the tires rotated until the recommended interval of 7500 miles (or whatever it should be) and by that time the fronts had worn to 5.5mm and the rears to 8mm, would you expect the safety systems to have stopped working properly?
It seems like you're trying to split hairs here.
Mazda has already answered that question for you. If you notice uneven wear before the rotation schedule, you should rotate them sooner. Otherwise DSC will not function normally.
Seems pretty straight-forward to me.
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