In Germany, my Origin, a spit roast (or hog roast) is called Spanferkel. That means as much as "milk piglet" or "teat piglet". Traditionally they get roasted and eaten at the age of six weeks with a weight of 12 to 20 kg.
So there You go, its not that uncommon, even the funny Germans do that like that.
Having such little piglets on a spit is rather found in the south of Germany, I am from the north and we would choose a bigger one around 40-60 kg, like what we do here as well.