Ditto Chip's and glen e's comments that it is all about RPM variance, and here's why that is important.
One importance of proper break-in is getting the piston rings to properly settle in, and getting oil to them is the key. This is done through the cyclinder vacuum that instantaneously occurs when you take your foot off the throttle, i.e., the vacuum literally sucks in additional oil into the cylinders.
I wonder if GM may be using the new-to-the-LT1 "piston squirters" to add additional oil, not just when the engine is cold, nor when the engine is under extreme load, but if they also programmed the squirters to add more oil all the time during the 500 mile break-in period? Even if true, I still belong to the "follow GM break-in procedures" camp, for there are many more parts that also need to be properly broken in, i.e., when I talked to previous Chief Engineer Dave Hill, he stressed to me that he wanted break-in to occur as spec'd for the differential to properly wear itself in.