on YT when the term teapot originated. It was one of those threads that pop up from time to time with people talking about their plus sized yorkies. If I remember correctly we were griping about how often a complete stranger approaches and makes a negative comment. Afterall, I've been told that my dog is not a yorkie, my dog is a silky, etc. and someone jokingly said when that happens to them the referred to theirs as a teapot. It just stuck. I don't use it outside of YT.
Chances are, the majority of both large and tiny yorkies come from less than reputable breeders. Many of the breeders who are breeding specifically for tinies are doing so regardless of the dogs genetics and health and then using their tiny size as an excuse to up the price. They advertise the dogs as "teacups". I've never yet seen a breeder trying to sell large yorkies as teapots and don't imagine I ever will.
I've got two big yorkies. One came to me as a puppy (I've since learned a LOT about choosing a breeder from YT...I was clueless then) and the other is a rescue.