like every other post in internet history regards breaking in an engine, there will always be the other method...
me myself and i, prefer the hard break in.
check it all over first, so yeah, valve clearances, decent MINERAL oil...
start her up and resist all urges to open the throttle. let it idle and go get a cup of coffee or a smoke or something.
nice and warm, take off in 2nd gear, holding the brakes on. full throttle. not about revving the engine, but about getting the maximum PRESSURE on the rings so they bed in to the honed cylinder bore. rings work by combustion pressure forcing them DOWN onto the piston, and OUT into the cylinder wall. a good five minute, full LOAD (not necessarily speed) first run.
then drop the oil and marvel at all the metal filings that are in it. and wonder why the hell manuals tell you to leave that dirty muck in there for the first "1000km".
fresh oil, repeat. repeat again. aim to change the oil every half hour for the first few times. whats a 4 litre bottle of mineral cost ya? $35? sweet eff all. once it STOPS coming out all glittery, leave it. go for synthetic if you really think it does anything other than cost a heap. and marvel at how long it tends to stay clean forever after. no piston blow by contaminating it. no loss of combustion pressure past the rings... an engine that seems to outpull all your friends that did take it easy at first...
then you can start jetting it, drop in those lumpy cams, etc...
they dont do it with chinese engines, but every reputable manufacturer actually does exactly this to every vehicle that comes off the production line. let them warm up gently, then full throttle the damn things, wind through the gears, make sure nothing explodes due to an overlooked flaw... far easier to grenade something in the factory, and reclaim whats left than to have a customer do it the day they buy it and replace the whole thing under warranty.