With respect the dealer won’t have a clue, if you know anyone with a mechanical engineering background ask them what they think on the subject. I would argue that a car actually takes longer to run in these days due to the use of synthetic oils and metal coatings that reduce friction. Its the friction that actually beds the components in so in reducing that friction the process takes longer. If you’ve had new discs and pads fitted to a car you’ll know that initially they don’t work as well as the old ones, thats because until the surfaces bed in you are not utilising the whole surface area of the pad and disc. It takes a good 500 miles of normal use to get them working properly, I would use that as a guide on running in your engine too.
Just my two penneth 😉