If you're sure an 0w-20 was used, I'd bet on lab error. Blackstone relies on human beings watching oil flow through a viscosometer for this measure, which makes error quite possible (same with flashpoint and fuel %, fwiw). If your driving patterns are anything close to those for previous UOAs you would expect considerable shearing.
If you didn't perform the last oil change yourself I suppose the dealer could've used a 5w-30 by mistake. On the bright side, given fuel dilution and how these engines can shear oils, an xxw-30 oil may be a better choice anyway.
Ah thanks for that information-- makes human error seem like the culprit in this case.
I changed the oil myself this time as well as the previous time. Nothing remarkable about this interval.. around 40 miles roundtrip of daily commuting with a couple of regional trips sprinkled in.