Well ALWAYS go by the manufacturer's suggestions for break in. That trumps the LHS's recommendations.

That said, some manufacturers ( such as Magnum ) recommend breaking in the engine with a Castor based fuel initially, then moving to a synthetic after the initial breakin period.

Castor produces a varnish like coating that turns back into a slippery substance when it reaches a high temperature, to it acts to protect the engine components from heat and wear during that important initial period.