I haven't gone to the site yet, but I may be more impressed if they showed pics of full grown pigs, those piglets are not any bigger then baby pot bellies.
I've seen small PBP, the ones we had as kids averaged about 30-40lbs. When I bought my piglet they had an adult (3 years old, they aren't considered grown til 3 years) female that was probably 40lbs, that is the smallest one I've seen in a very long time. The breeder had gotten her as an adult and admitted she didn't know if it was all genetics, or if she'd been stunted by lack of care. When I saw her she looked healthy and well proportioned (seems like when they are stunted (not just pigs, but any animal) their proportions are out of wack), so she may have genetically been one of the smaller ones. When I was considering a second one I was going to get one out of the girl bred to a white w/ black spots male. I know another lady who's pigs were about 20lbs when I saw them at 1 year old.
Other then PBP, I've haven't seen many truely miniature pigs, I did have 3 female pigs that were given to us when we were kids, they were about 35-40lbs fully grown, they weren't PBP, I have no idea what they were exactly. They were kind of ugly and they and their babies were not as friendly as PBPs (and that includes the one that was raised on a bottle (his dad was a PBP), he was a cute as the PBP, but not as friendly).
If I was looking for a miniature pig, I'd search for PBP breeders, see the parents and ask about ages (3 years is considered full grown). Read up alot, there are several red flags to avoid (for example if the breeder advises you to starve the piglet in order to keep it small) and pick one you feel comfortable.