I dont believe for a second that Sean isnt saying anything about the issue because of any NDA. One, the game launched, and two, he said time and time again for people to not buy his game hoping for this, or that thing other games were doing. "dont buy my game, it isnt X" wouldnt be expressed even in thought If he had an NDA haning in his head. From What I see, there is two possibilities.
1: He was lying through his teeth, and the silence is to make as much sales as possible, and in case of the PC release, make people play more than the 2 hours eligible for a refund. from what I know, preorders are refunded no questions asked by valve, arent they? Its a bit harder after the 2 hours unless the dev talks to valve to grant the refunds, something is a lot more rare (Arkham Knight levels of fuckery).
2: There is some form of multiplayer that isnt working at the moment, and they are not responding because of insane amount of crunch time and they generally being dead to the world until they make the date for PC release. (I dont believe its "adding features"), dont remember any game dev saying they are adding a new form of AA or ATI compatibiliy drivers a week before launch.
Lying or not, we saw those people are on some serious crunch since the game went gold for PS4. Like, unhealthy levels. The silence could be this, our it could be that he was lying, and to be honest, that would tank my faith in the industry for good. That a person could go on live television and lie to the face of Colbert. I am not even american and understand you just dont do that unless you have no morals whatsoever.