It's pretty significant because it's the first example I know of where a manufacturer, in this case GM, decided to change, and in no small way, the running temp viscosity of the recommended engine oil in response to experienced bottom end bearing damage in engines originally specced to run a light oil, specifically 0w-20. It is a tacit admission that the "lighter" engine oil is not seen by them as adequate to protect their engines under load. There will certainly be some who see this as a vindication of their opinion on what oil ought to be used in high performance engines.