Bob,

You wrote that an engine manufacturer's instructions should be followed.

Yet what many manufacturers write may not not be as clear as Jett's.
Also, specifically for OS, the manual says to cycle between four-cycle and two cycle, only to be contradicted by the OS Q&A, Bill Baxter and AnnMarie Cross, who say not to four-cycle it at all during break-in, if the engine is a tapered-bore.

I would say the break-in method should most often be determined by the type of engine, more than by its often unclear, or erroneous manufacturer.