Could also be dealing with a manufacturing defect or just an engineering quirk of this particular tire model.

Toe settings are a funny thing, though. Toe being out by .1 degree on one side would probably have the effect of making the whole back end of the car "dog track" just a little bit so that the net effect was "equal toe" on both rear tires in their direction of travel. (just like what happens in the front of the car when toe is off on one side, except that the steering wheel angle compensates in the front) So, I could be wrong, but I don't think that toe being out A LITTLE (.1 is a little... not like half a degree or something) would cause wear on one side, but quite possibly on BOTH rear tires. Where things would get weird there is in cornering, the car would handle completely differently when turning in one direction vs the other.

I'm going with weak shock... and still a little curious about the ABS idea. Regardless of how those "flat-spots" started their life, they would behave as flat-spots under braking and want to lock up.