Why isn't creating a topic below those sub-categories locked since it's not really needed, as there are more specific areas for such subjects. If it has any use to create a new topic, what would it be?
When Digiex started out we had little Xbox 360 content so it was all in one section, like it is with the PS3 stuff. As the forum grew sub forms were created to organise all the content, its simply just a setting that looks to have never got changed after the sub forms were created. You have a keen eye to spot that, its been changed now.