It's possible of course, but something doesn't ring true to me.
If, as you suggest, those 6 tracks were the most advanced, that in-turn means the other 13 were well under-cooked.
Should that be the case, the mid Nov. release date wouldn't have even been remotely close.
So either the initial release date was deliberately a complete furphy, or they are keeping the other tracks close to their chest for different reasons.
Edit.
Sorry, I just realised I've used some Aussie slang.
Furphy:
"a rumour or story, especially one that is untrue or absurd."