I think 10-12 weeks is ideal and preferred. I guess 8-10 weeks is okay if the pup is sound and the owner has experience with caring for young dogs.
But I definitely think 6 weeks is way too young. I know some have not had any problems getting them at like 8 weeks which is still too soon in my opinion , for a dog of the yorkie size. I would just prefer not to take the chance. Hopefully you can wait 2 to 3 more weeks. Good Luck with your new pup!
Welcome to YT.