This is not actually true. The engines are not run very much at all before they leave the factory. I think they're all started, but the average motor is not run much at all before it's installed in a car, equivalent to maybe a couple miles of driving. Once they're in the car, the mileage on the odometer when you buy it is really how much it's been driven.

Toyota (and all the OEMs) have manufacturing processes that make sure that every motor is put together exactly the same way, and they've ran huge numbers of those motors on test dynos to find the best way to put them together for longevity.

I have a college buddy who works as an EFI/OBD calibration engineer at Toyota's LA facility. His office is a warehouse with, IIRC, something like 100 engine dynos and about half as many chassis dynos. They just run engines all the time to statistically develop the most reliable/powerful/efficient/clean control strategies. Every OEM has several facilities like this around the world, Toyota has at least two in the US.

 

This is what I had herd from one of my gurus, he told me that they have to break them in to reduce user error, mostly setting the rings. It would be the same thing they do at Harley Davidson run them for 5 min to set the rings and journals to insure it will work correctly.

 

I heard and seen the dealer turn on the car at delivery and just leave it on for hours.