I find it funny they specifically are about pigs because just the other day, a vegan community posted a chart of the negative environmental impact various farming industries have, and pigs were the lowest impact when it came to animal farming. It was only slightly higher than farming soy.
Not sure which post you're referring to, but from Our World in Data, pig farming generates more emissions than farming chickens. They are lower than beef, but that's not saying much, since beef is an order of magnitude worse than most other foods. Pig farming also generates four times more emissions than soy.