Unwritten rule to selling a 4 door

I don't think they are trying to be deceitful. Just a few lazy camera shots. They do describe 4 doors and show that clearly in one photo.

As for the "not a Duster", I have seen many times where sellers say they can't change the title, so they have to put a caveat in the description when they find an error. Probably the case here.

Anyway, they would need a lot more effort and polish to get their asking price, and even then they can't force-feed it, the market will decide a fair price.