Question for the autistic people on this thread: Is it useful or helpful to know how to interpret this kind of NT duplicity?
Yes it’s helpful to know but knowing isn’t quite enough.
Or does that sort of issue not crop up much?
Oh god, you must be kidding! Constantly. It’s pervasive 
Should I teach DS this stuff or let him zone out over it,
Definitely teach it to him.
Even knowing it, it’s still hard. I’m quite attuned and accustomed to passive aggression, deceit and dysfunction (thanks Mum) but even in the full understanding of the game going on in front of me, I have limited tolerance for it. After a certain length of time it fries my brain. It’s mad, inefficient and upsetting.
If youve seen the Ricky Gervais film “The Invention Of Lying”, that might give you an insight 