There are two break-in procedures, one for cams, another for rings. The 15-20 minute fast idle procedure is to establish a running relationship between a flat-tappet cam and new lifters. Roller lifters- - - -no problem with idling from the get-go. Perfect circle used to recommend a ring break-in procedure consisting of 10 full throttle accelerations from 30 MPH to 50 MPH to let compression and acceleration cylinder pressure force the compression rings tight against the cylinder walls to scuff them into a running fit with the crosshatch in the cylinders.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!