My bike had 1 mile on it when I picked it up in March. It was winter and I don't think anyone took it out for a shake down ride; if they did it was a short ride. And I agree with you, the rings set within the first 20-50 miles.
-Bill-

 

And, if the rings do, in fact 'break-in, in the first 50 miles??? Break-in is about the whole machine. How the gears mesh with each other in tranny; bearings making their wear patterns, belts and all kinds of things spinning for the first time....has a part in this also.

and... sometimes this doesn't work out quite so well...