I would guess it is just an oversight as the forum guidelines were probably written long before T2's recent hissy fit.
Well that would be my guess as well and is exactly why I asked the question. There's a thing called plausible deniability and that's an incredibly useful defence in this kind of situation.
If you have a rule that says "You can do something wrong", then if something does go wrong, you are accountable. If you have a rule that says "You can't do it" and then fail to enforce that due to... excessive forum requirements, insufficient numbers of staff/moderators, yadda, yadda, yadda... you have plausible deniability, it's a layer of protection.
It gives you the chance to say "You're right, we should have been more vigilant and we will be in the future... we're sorry.". You don't get that option if the rules basically say "Yeah, go ahead, break those rules".
I'm pretty sure most people's reactions to this thread are potentially hostile and that's because they don't understand how things work. I do, I have been on both sides of this fence. I am a modder, I was (and to some extent still am) a game developer... and I ran my own games company. I tried to fight for the modders on 5Mods and lost but if I can find places where a nudge in the right direction, gets a site on the right side of a protective fence, then I will happily accept the hostility, if the site takes notice, understands why, and is pro-active as a result.
If I have to sacrifice my presence here, because people get annoyed at me pointing these things out, then so be it... If the community wins and has a better chance of surviving the scrutiny, I will happily take the hit.