I think actually the people who think there are teacup pigs are the people conned into buying ones sold as such. Until their “teacups” grow to hundreds of pounds. My impression is that the breeders selling animals as such in fact usually know better.
Your linked cite gives all the signs of being one of those online sellers discussed in the articles.
There was no real reason for selective breeding of cats for size, so the size remains more or less the same in all breeds. Furthermore, an average cat is in the range of a smaller dog, so why do yu want something smaller? It is fortunate that too miniaturized cats do not exist, because such animals mostly develop health problems.
Ignorance fought. 
@correlophus:
Yeah, but just think how effective they could be at mousing if they could slither inside the walls like the mice. No more mousey sanctuary!
There was that one time where a Great Dane and a Chihuahua were bred…
I don’t know about the OP’s experience but it seems like it’s much easier to control the breeding of a dog than it is a cat.
If you want something to get into the walls to catch the mice, use a ferret.
Just for the record, I personally don’t want a smaller cat. I don’t think my sister-in-law actually does, either. I just got curious once she raised the concept.
Indeed, the ferret is as domesticated an animal as any other domesticated animal … and this was the reason … although the ferret is good at catch and killing rats and mice … they also spook the vermin out of their warrens and into the clowder of cats (or the backpain of dogs, whichever is handy at the time) …