I know that nowadays we don't "run in" the engine and gearbox etc. I was, however instructed not to labour the engine and keep the revs down for the first "couple of hundred miles".
What is the score? Do we "run them in" or not?
I think the instructions you were given are in effect the 'running-in' instructions for the modern engines.
Bear in mind that your tyres also need 'running-in' for a similar period to achieve maximum effectiveness.
My previous car, a Toyota Celica T Sport had instructions to keep revs below 2000 rpm in all gears and run-in the tyres for a few hundred miles before squealing around corners. It was happy doing 8,200 rpm in all gears later but some passengers thought the engine would jump out lol.
I would think following something along those line would be of benefit to your engine and gearbox although, I don't know what maximum revs to suggest. I just tend to keep this engine running quietly.