Let's explain why you break in a motor, then you'll understand the rational. When you receive a new motor, the parts that make it up are fresh from the CNC or mold process. The tollerances are good, but they aren't great since they are now mated up against a piece that has been cut at a different time and different piece. Because good compression is caused by making sure the piston is tight, a lot of times the cuts are done so that the parts fit real tight. Friction causes wear and every motor will have wear over time. The idea is to use this wear to, in a sense, grind away the imperfections between the mated parts so they wear in a certain pattern that makes the tolerances even better. Once a motor is run for a while the wear loosens the tightness and "breaks-in" a motor. Since a motor is at its least optimum "fit" in the beginning, you want to slowly ease in to this. After all, you're wearing away metal on metal. If you do it too fast, you'll rush the motor through this step and introduce much higher heat, expanding the metal and introducing all sorts of accelerated wear. If you're not tuned right, it could be really bad. Go slow and control this wear process. Motors don't know what brand they are and physics don't either. The same principles apply to all motors. Big 1:1 car motors, motorcycle motors, etc. Why do you think in your normal car your manual says take the first few thousand miles easy. If its not required, the factory does it for you, either way take it slow.
Finally, I'm running a RB motor I got from Chris Tosolini. He's one of the best in the world and he helped me break in mine; slow. Good luck.