It's so hard to tell or to know if the Breeder is truly honest or if there is a mix in the parents past! I was looking at pics online of Chorkies and of Yorkshire Terrier puppies and DANG! it can be hard to tell even in those pictures!
Here is my advice after looking at the pics and what others have to say, I say watch the pup grow for the next few weeks, then make your decision. He is so young right now it's really hard to say either way.