I have and continue to do as much reading/research on our Favorite Breed, and find that there are many commonalities in the Terriers.
WAY back when Yorkies and others were "constructed", it was important that when tasked with their "duty" of ferreting out varmints, that they did so without human intervention. ie: "set it and forget it"
This "feature" about Terriers in general, is what I think to be the cause of much of the notice about their personalities. We as humans appreciate that others are different than we, and subsequently, appreciate that in your Dogs as well.
I do see that from the information I've accrued, that Yorkies seem to have a bit of an edge when it comes to Personality, which equates to individually. This, though inadvertent, is what makes them SO special.