Perhaps other breeders here can confirm, but I have also heard that this bottom line can also vary by breed or breed type. Shibas, for example, being a more "primitive" breed, also have a particular play style that causes them to play ROUGH, especially with their own kind. So in such a case, is it better to keep them just a little longer (say, up to 10 weeks) so that they learn from their own siblings just how rough is too rough, or is it better to take them from their litter as soon as possible to teach them that bite inhibition with other humans and dogs means a different thing from other puppies?
Seems to me also that this is when an experienced breeder is necessary. Every single week is so critical when they're that age!