I was trying to find the hidden loss because if anything has 4 panels of any shape my brain has been rewired to think it's probably hiding that damn meme somewhere. I'm still not convinced this isn't it.
I didn't even know about the Pullman, but now I've found my new religion!
EDIT: Nvm, I guess it's the common sandwich shape. I just found some images that were incredibly perfectly square and thought Pullman were these particular perfect shapes that required some forbidden technique.