i think you're going to hit a bit of a philosophical wall here. what he's saying is, with a small carburetor, you can't break in your kit properly because you can't hit high rpms. so he's clearly a "hard break in" person: someone who thinks that to get the rings to seat properly/the cylinder honed, you have to do some HARD riding during break in. virtually all experienced two stroke tuners i've read say the same thing. on the other hand, it's very easy to over-do the hard break in routine . . . in which case you end up seizing your kit, which is a lot worse, obviously, than not breaking in quite as well. for that reason, cautious types often opt for the soft break in procedure, where you don't do any hard riding for the first couple hundred miles of the kit's life, that way insuring that you don't fuck it up. after a couple hundred miles, the cylinder walls have been honed down well enough/had enough oil worked into them that you can start riding harder, though they're not broken in perfectly, like they would have been if you'd done a hard break in.
so one way to look at it is, your 12mm carburetor is an insurance policy against you fucking your kit up by revving too high for too long during break in, since with such a small carb, you can't. after 200 miles, maybe you'll have saved up enough for that new, bigger carb, which you can then run with glorious abandon, without any fear of seizure (assuming you jet it properly). the other way to look at it is, you can't possibly break in your kit speed racer-level perfectly without a bigger carb to allow you to rev higher. but a lot, a lot of people seize their kits during break in, so the cautious line of reasoning is worth consideration, i think.
sorry to write such an essay!!