Can you link to that FAQ? I can't seem to find it. Thanks.
This is where I got the text from. This is nice to know since the FAQ elaborates that it's only considered TWF when you are making more attacks than what your iteratives allow, and it requires that you use separate weapons (or for the case of Unarmed Strikes, requires that you have at least 2 separate limbs capable of carrying out those Unarmed Strikes) for each iterative set you acquire from TWF; this also means you can't sub out different weapons for each iterative, you choose one weapon, that makes all of the attacks of one set of iteratives, and then you have your other weapon make all of the attacks of the other set of iteratives.
I'll also note that the FAQ says you can draw weapons mid-iterative as far as your normal attack scheme is concerned, whereas the same language for that sort of subject is absent when they get into the TWF attack options, which further supports my theory, in that you must be able to take all of your attacks simultaneously before you can take the TWF option, which is another reason why a Greatsword with Spiked Gauntlets/Armor Spikes aren't allowed, meaning I couldn't use a Spiked Gauntlet, or Armor Spikes with a Bow, but I could certainly use a Blade Boot or a Kick from Unarmed Strikes.