Well that was a good laugh for a Monday evening. Forum hyperbole and conjecture at it's best.
I went down to the M factory a couple of years ago with a friend who has a big composite technology firm and he had a meeting with some of the bosses etc. I wondered around asked some of the engineers this exact question having owned a few M cars in the family some from new.
They leave the factory with fully synthetic oil. Not Joe Gibbs running oil, mineral oil etc. The M engines are hand assembled but factory line built. These are not 50k honed bore blueprinted engines as much as the die hard M fans would like to think.
The reason they ask for a 1200 mile running in is because they know a lot of users won't follow the instructions of varying engine speeds, not accelerating harshly etc during the running in period. This causes heat build up and although the tolerances are pretty good as most factory built engines are these days there may still be expansion causing increased wear in the early periods. The 1200 mile service is purely precautionary due to the lowest common denominator who won't follow the guidelines. If you follow the guidelines and the engine beds in well there is no need for an oil change but for the manufacturer it's simple precautionary guidance.
Also random engines are picked from the factory and run on an engine dyno to pretty much full engine speed but not for enough time to cause full thermal expansion so something like 1/5 M engines will have been ragged before you've even driven your new M car