My Z06 had very specific instructions. None of it involved WOT until 1000 miles.
Also, the rings are pressed against the walls most when the engine is in vacuum. Engine-braking from a sensible rpm is the way. Not revving to the stratosphere.
During break-in of my Z06, I noticed for the first few hundred miles, a lot of soot on the tail pipes, as well as oil consumption (about 1/2 a quart total, in 1K miles).
After about 7-800 miles, the soot stopped. I tracked oil usage after the first change I did, at 1K, and it never used another drop that I could tell.
The engine definitely needed breaking in. Beating on it wasn't the way it was to be done. When you do this, you spike surface and system temperatures beyond normal maxes, because the increased friction of rougher surfaces will do that. After the engine is broken in, these surfaces play nicer. The same happens with the transmission, and the diff gears. The real bug in the ointment is the brakes...which should be broken in HOT for some systems (carbon fiber rotors/ceramic pads are a perfect example). Gears like a gentle break in, brakes like a hard break in, and engine components vary, but I have found a sensible break in is best (driving in moderate city traffic, and engine braking, is a great method, actually).