The white should go away as the pups grow, this is why you normally do not see it on adult yorkies. Lacy's mom is correct and was quoting from page 205 of "The Complete Yorkshire Terrier Book" by Gordon and Bennett. This book is like my yorkie bible and explains everything about yorkies.
Breeders look for this but it does not indicate a coat, as an adult, that will be of great quality - but should have a lot of hair. It might not have the sheen/shine but may have a lot of hair.