Yes pigs do eat pigweed especially when the pigs are out in the wild.
I've heard that pigweed is actually toxic to pigs but pigs out in the wild eat the pigweed and they seem to be just fine.
Also when I grew up on a farm we had pigs and the pend they were in had pigweed around the fence and the pigs would eat on the pigweed.
Those pigs lived long and never got sick from it.
Well the pigs lived long enough until my father slaughtered the pigs for the meat.
My dad raised pigs, cows etc all for meat and even chickens.
The pigs consumed the pigweed and they were just fine.