I don't think anyone would have problems with their engines if broken in on synthetics. The argument seems to stem around ring seating and the superior lubricant properties of the synthetics. Supposedly, if you break them in on synthetics, the rings never get a chance to seat properly, and thus never really develop their full potential in regards to power output. If you stick with regular oils, you don't get the superior lubrication and loose the increased lifespan the synthetics would give you. So their solution is to break it in on regular oil to let the rings seat properly, then switch to synthetics to reduce the wear on the engines. When to make the switch doesn't really matter, or even if you switch at all for that matter.

Frankly, I don't think the engines in our use ever see the end of their service life. We just don't use them enough to really reach that point.