He is right for the most part.
I've got a speed shop about a mile up the road that I hang out in sometimes. They've been building and racing drag cars for about 25 years now I believe. They will tell anyone the same basic thing. Varying your speeds and throttle usage for the first few hundred miles will greatly increase a PROPER break-in. Getting on it really hard about 20-30% of the time helps the ring seal process along greatly. The only thing I have ever avoided was stomping it in 1st gear for the first few hundred miles as this is the heaviest load you can place on your engine without towing something behind you. Simply stated, new metal is weakest. There is a great deal of truth to "Heat Cycles". It is the cycling between hot and cold that tempers metal (as well as glass). If you were to ask most people who've been involved in any kind of racing, and asked them if they would rather have a green-block, or an older well used block, they'd take the used block simply because the block has been tempered from use over a long period of time. Cylinder shafts can always be re-honed, and the blocks can be Magna-Fluxed for cracks, and you end up with an engine block that is MUCH stronger than any green block you can buy.
I've got a speed shop about a mile up the road that I hang out in sometimes. They've been building and racing drag cars for about 25 years now I believe. They will tell anyone the same basic thing. Varying your speeds and throttle usage for the first few hundred miles will greatly increase a PROPER break-in. Getting on it really hard about 20-30% of the time helps the ring seal process along greatly. The only thing I have ever avoided was stomping it in 1st gear for the first few hundred miles as this is the heaviest load you can place on your engine without towing something behind you. Simply stated, new metal is weakest. There is a great deal of truth to "Heat Cycles". It is the cycling between hot and cold that tempers metal (as well as glass). If you were to ask most people who've been involved in any kind of racing, and asked them if they would rather have a green-block, or an older well used block, they'd take the used block simply because the block has been tempered from use over a long period of time. Cylinder shafts can always be re-honed, and the blocks can be Magna-Fluxed for cracks, and you end up with an engine block that is MUCH stronger than any green block you can buy.