i found a 1903 published
google book about British dogs. YT is on page 582. The author, William Drury, did mention about a theory of the YT breed with a dash of Maltese Terrier. However, at the end of the YT section of the book, during the time of publishing, there was a demand for silver yorkshire terriers and even had a show class of its own. The author wrote that, "
As, however, these for the most part are poor-colored examples of the true Yorkshire Terrier, it does not appear compatible with a desire to improve the breed to encourage them." (page 597)
IMO YTCA just protects the true Yorkshire Terrier as it was bred and created to be. With the theory from 1903, there is a chance that the dash of the maltese terrier blood can bring out the parti.
Whew... anyway, it was a nice read, learning about how they took care of the coat in the old-school fashion. Nice natural approach with the oiling and the yorkie diet.