Well there are always different cases, sometimes dealers take hobbiest to japan with them, with the understanding that the fish will be directly shipped to them, once they have cleared, APHIS, Fish & Game, Customs...
But if a dealer gave you the option that they would Qt your fish, I would let them do it, if there was the understanding that if something happened during QT or KHV testing that the dealer would compinsate.
With so many hobbiest going to japan these days, some dealers may not offer any compinsation, if the fish did not survive through Qt. So if that was the case you might as well take them home at least you could keep a close eye on them and treat accordingly, and as long as you have access to KHV test them.
I know some hobbiest will do the heat treatment regiment, for me personally that is just not enough, I still want the test done.
Some dealers don't even know how to properly QT fish, I have seen this way to many times. Fish come in fish go out, no testing, no scraping, no parasite treatments nothing nada.