Upload & Sell: Off
How does your coverage compare to previous wedding sets they've seen of yours? If they'd seen heaps of group shots from your previous weddings, they may have been looking for that style of coverage.
However if that's not the way you normally work, then they should expect the style of coverage that you delivered
- agree that you can't be expected to read their minds
It's a good idea to find out who all the 'important' people are (i.e. close friends and family) and make a point of getting plenty of shots of those people (though you probably already did this)
Tough situation; it does sound like you did all you could to get their input, and you have a written pre-wedding questionnaire to support your position.