It's less about size and more about enthusiasm (or acting, at worst). Yeah, having a 25cm dick is definitely a big plus for doing porn, but that doesn't matter all that much if you can't perform on camera, either due to shyness (so no enthusiasm) or for lack of ability to act. If you can't really pump hard and the girl has to put on a screaming show to sell us something, are we really enjoying this?
The case of her boyfriend is made worse, because not only is the dude clearly WAY TOO FUCKING shy, he's also fat and small dicked. When he was presented with the triangle and told to pick 2, he got too shy and the choice defaulted to nothing on all categories.