I firmly believe in break-in of a new motor, but I personally don't feel "babying it" is the best way to do it, at least in the circles I run in we don't do it that way.
The beauty of doing it on a dyno is it is broken in under load, so your "gentle" pulls aren't as gentle as, say, cruising at 30 mph in an automatic transmission equipped vehicle. This should, as I see it, shorten the break-in time required considerably.
It's similar, to my way of thinking, to how I have broken in marine engines, where the prop in water pushing a relatively heavy boat (that is, one whose weight is appropriate for the engine size) is always putting the engine under load.
I don't remember the Yamaha 4-stroke procedure exactly since it's been about five years since I did my last one (a 90 HP Tiller 4-stroke) but it wasn't that many engine hours before you were running it a Wide Open Throttle (WOT) for brief periods and not many more before you were running it at WOT for as long as you want.
That is considerably more severe than taking it easy for the first 2000 miles in a car or truck. 1 always based one engine hour to be equal to 30~60 miles for a 4-stroke motorcycle break-in schedule. That also correlates well to Yamaha's guidelines; 10 hours being the equivalent to 300~600 road miles, making almost any engine ready to run as desired in 10~20 hours.
I am also a believer in that you should break in the motor in the manner you intend to run it. If it's a high performance application, you should be making runs under load to redline as soon as reasonably practical. Although I don't do it, I do know people who have built many well running motors who run them hard right from the outset after a very brief break-in procedure and early oil change (1 hour or 60 miles).
My break-in for a road vehicle is moderate operation preferably under load as much as possible with varying the cruise RPM often in the first 60 miles or 1 hour, an oil and filter change, run about the same with occasional very brief runs to WOT in the next 500 miles or 10 hours, oil and filter change, then run as you expect to operate it for another 1500 miles, oil and filer change, then go to your desired Oil Change Interval (OCI).
There are about as many break-in procedures people use as there are engines, almost. I don't expect anyone to copy what I do, if only because they probably have their own ideas.
I do follow the manufacturer's recommended procedure for early operation though in a factory fresh mill. But I follow my own ideas for rebuilds.
I doubt the dyno break-in is anywhere near that long ... anyone familiar with the programmed break-in regimen care to comment on how long it takes?