Service manager. His department gets paid for doing service. On warranty work he gets paid by Mazda. There could be a connection between this and his advice.
Yep, and again, a service manager is not an engineer. The break-in is drive-line related. Even mating of the brake pads and rotors (every company has different specs on this, GM's brake break-in specs and their driveline specs are at complete odds with each other on the ZR1 and Z06 Z07 package, lol!), the diff gears, the wheel bearings, everything.
That said, I did lose about 1/2 quart of oil in the first 515 miles I drove my Z06, per the dip-stick. After that, I changed the oil, and never noticed another drop missing. Further, the tail-pipes never sooted up again like they did that first few hundred miles. The rings legitimately did seat, and my car was run at the factory a lot longer than 15 minutes. I know, because I was there and saw it.
No-matter how well polished parts are, they have high and low spots until they are lapped in by actual USE. When you abuse the vehicle before this happens, all the force of part interaction is translated to these high-spots. More metal than necessary is displaced in this manner. The result can be minimal/none, or it can be meaningful over the life of the vehicle. As micropolishing and other things have advanced, I lean toward it being minimal...but still, as pedantic as people are on this forum and others...minimal matters to 'em! break the vehicle in the way the manual/company making the vehicle states to!