I've never heard about that before. Every breeder I've ever talked too, all the books I've read and every website I've ever visited, says something between 8-12 weeks of age.
Over here most people let the kits stay with mom (and often dad) until they are 10-12 weeks old. Some very mature kits can go to a new home when they are 8 weeks.
But almost every english and american site/breeder takes the kits away between 8-10 weeks and let the kits stay in their own cage until they are between 12-14 weeks.
I really do not think the breeder you've found is a competent breeder.
Furbreeders are known to take the kits away from mom before hobbybreeders do. They do not remove the kits before they are at least 7 weeks of age, and they normally say 7-8 weeks.
Try researching how early other breeders take away the kits. You could also try and call other breeders.
Unfortunately you often have to know every thing when it comes to chinchillas. When you say a "licensed professional" I'm guessing you are talking about a vet. The problem is, that often vet's do not know enough.
Things work a bit different here when it comes to vets I must admit, but in my experience the more you know before you go to the vet, the better. The best thing is if you already know what the vet should look for and say. Sad but true.
Oh, and I'm not mad or anything
I'm just worried you are going to get a problem animal. You are going to have a lone chinchilla, that's been removed too early, and I'm worried you are going to get a chinchilla that's not sure if it's a chinchilla or a human... Some very independent kits also have a problem with personal hygiene. They can have a lot of pee on the tummy, and only mom or dad can clean it from them...
I've also had some very independent kits. We couldn't keep them in the cage, and they only got back in when they wanted some food, but they were not mentally ready to go out on their own when they were 4-6 weeks...