I had a problem with this when I bought my 2002 Sienna in 2001. The manual said to break the engine in by driving at varied speeds for quite a while, but not driving fast. That certainly implies a break-in, or at least that is the way I took it.
If it is indeed a break-in, then something has to change. A motor can't break-in without polishing or smoothing or changing tolerances somehow, thus there has to be something metal moving around in there. Maybe not filings, but at least powder of some sort.
I knew in a few days I was going to be driving across the country, and it was going to be at 70 mph when the law allowed. So, I went on drives north of McAllen on less busy highways, for example out by old Moore air base, changing speed as they said, to get my miles on.
And, at 1,000 miles I took it to the dealer to get the oil changed, and they promise to use all genuine Toyota parts. The guy looked peeved that I would change my oil at 1,000 miles. And, when I picked up the car, it said Pennzoil, which I am sure is not a genuine Toyota part, the last time they ever changed my oil.
To me, it was simple. Either the car needs a break-in, or it doesn't. And, if it does, then there is metal in some form, even if only microscopic powder form, because break-in has to do something. So, I changed the oil.
And, it was my car and I can do that, right or wrong. And, whatever opinion you have, I feel the same is your right. Synthetic; dino oil; change every 3000 miles or not until it blows. It's your vehicle, unless you pass it off as a used car. That is exactly what liberty is supposed to mean. People talk a lot about a free country, and it has long been apparent most have no concept of liberty as also applying to your right to change you oil as you want, without being hounded and harassed by those whose views are different.
The other issue is using synthetic. Some folks have said not to put in synthetic until maybe 50,000 or more miles, because if you put it in too soon, the motor won't break in.
Let us use our brains for a minute to think about that. I admit they fooled me, too, for a while.
If, and I repeat, if, the synthetic makes things so slippery it can't break in, then it sure seems obvious that it makes things so slippery that it really doesn't need to break in.
Once I realized this, I realized this was another of those myths made up by those who really don't think about what they are saying.
If I ever buy another new car, it will get synthetic at the first oil change.