I think perhaps that the distinction needs to be made with regard the 'goals' and methods.
I don't think DD1's Communication group is intended to teach her how to play hide and seek. I don't think it's intended to teach her anything 'concrete', but it is intended to teach the skills that lead up to purposeful, meaningful communication.
Children with ASD may not be able to learn effectively about the social nature of communication just by exposure. But they can learn skills explicitly, and actually, whilst at a later stage the 'whys' need to come, the first step is knowing 'what'.
So, a child being taught 'first do this, then do that', is IMO just as valid as 'it's really pleasant for other people if you listen to them when they speak, think a little about what they say, and give a response that is related to what they are talking about'.
In a social communication group, the children are being taught the skills of listening, responding, turn-taking, looking, etc. All of which are pre-requisites for communication.
Btw, DD1's school is a special school, but 94% of the children there have ASD as either their diagnosis, or part of their diagnosis (DD1 is part of the 6%).