I am an advocate of the 'ring seal' run in. But I used to race bikes so could see the benefits.
The soft break in method is a little old fashioned, stems back to older machining techniques that left rough surfaces that required 'bedding in'. There were surfaces that potentially broke through the oil film and caused metal on metal contact.
Todays modern engines are machined to a much finer tolerance, and have both improved oil contol and oil technology. So the old 'bedding in' process is no longer important.
For most manufacturers new engines are run on an engine dyno and then again in the finished car on a wheel dyno.
They test for power on these tests, as it is the best engine 'quality check'. So in truth that engine you are babying started life running at full power within a few minutes.
So why the manufacturers running in guide?
A new car is not just a new engine. Brake components need bedding in, tyres need the release agent scrubbed, clutch discs need bedding, etc so it is common sense to drive well within the limits of the car until these systems reach optimal performance. This if done correctly only takes 50 miles max.
It is not difficult to imagine why a car manufacturer might recommend a running in regime. Theses reasons have little to do with mechanical sympathy.
At the end of the day, it is your car, and whatever method sits well with you is the best method
