They state with only a few examples that medieval pigs were different. Pigs come with such variety it is hard to say that current depictions are wrong based on such a small sample.
Using modern pigs gives a false impression even if I’m wrong about that because until after WW2 pigs in the West that were raised industrially were raised for lard more than lean meat. There have been huge changes in what most pigs look like in living human memory.