Exactly. As Shad said, it's marketing bullshit.One pop door per 600 birds. 9 hens per square meter. That's a pretty twisted use of the word "free."
Then there's the issue of what they find if they do find one of the pop holes and do venture through it: Bare exposed ground in most cases, not the green and shady light woodland that might appear in the image on the carton or in the customer's mind. That's the reason why backyard birds dash out as soon as the door is opened and industrial 'free range' birds don't.