Old thinking regarding break in is that you need to baby the motor to seat everything properly. The reason break in is recommended as well as an oil change early on is due to small metal fragments from the fresh parts that can be caught in the oil/motor. The break in is not so much to seat the parts which AMG already does before you get the motor but to protect from an early failure due to running the motor hard in case metal shavings were to get into the motor.
As a matter of fact, a hard break in will usually result in a stronger motor with properly seated parts. Mercedes tests these motors hard as seen here. Don't fear running your own motor hard, it will love you for it. Plus, Mercedes already did.