"In battle, you switch from offense to defense and vice versa. The only character that the player is in direct control of is Noctis, however, the other characters will act according to tactics that the player set beforehand."
Direct control and Playable characters are two different things. Tabata was explaining that when you have control over Noctis you can't control the other members. SO the Gambit system comes into play so you can change their behavior in battle. They never said " Noctis is the only playable character. They only said in a nutshell, " When controlling Noctis you cannot control the other party members. ( Basically, a FFXII battle system in a action format.)
This is what Duckroll says from Neogaf ( an Admin):
(I checked out the 4Gamer interview, and regarding the playable character thing...
When Tabata says that the player only controls Noctis and the other characters have AI commands, it sounds more like he's describing how the system works as it is. In the demo shown so far, the only playable character in Noctis. It could be that they have removed character swapping, but it could also just be him describing the fact that as an action RPG you only control a single character. At the same time, he does talk about how the game is very much about Noctis and his friends "helping each other", so that might be why only Noctis is playable.
The important points he highlights is that there will be AI settings in the menu which can be changed, and the player will have a degree of control over the battle flow.")
