The factory functions as a reference for writers, and that's about it.
If you tell me 'my blaster does this' in a factory sub, that gives it a bit more legitimacy than just pulling the blaster out of nowhere and telling me it can shoot better than your average blaster pistol.
If you don't want to sub anything, you don't have to. If you tell me your blaster shoots lightning, most writers are willing to respect that without need for a sub. But if you wanna get into the nitty gritty of what your blaster does, then I'd recommend a sub in the factory. Same with the codex. It's all reference material for us nerds who want to be able to look at the strengths and weaknesses of an item, and see that the judges approved it.
I think the only exception is SSDs and Superweapons, which definitely require a factory sub and admin approval, or else you saying "I blow up this planet with this superweapon I've had all along!" is just gonna get shrugged off and considered non-canon.