So, if they don't limit what modders can do, then the vast majority of mods WILL break the console version if people download them. Who is going to QC if they will break them or not if they are distrubuted freely? Give me a break. So, the only way they could ensure that nothing released through their database would break anything is to not allow anything to be created that could break it.
I have downloaded about 30 or so mods and so far none of them have required anything but placing them in the data folder. And what exactly do you mean by break here? Because I'm pretty sure mods can not permanently "break" the game.
Hell, maybe they could even run a check to make sure it is compatible, or if that is imposssible, just have a "console compatible" checkbox for modders to fill in on sites you can get them from.