Linguistic and communicative competence
Not at all the same thing
Communicative Competence is often counterposed to Linguistic Competence on the assumption that it is more relevant to the real world of children who are sometimes very difficult or impossible to understand. That assumption is just an assumption. It needs to be carefully tested. It may not be appropriate.
There are the moral imperatives of truth and sincerity. Truth depends on exact meanings.
There is the pragmatic assumption that information is given to inform, not to mislead or deceive. Information also depends on exact meanings.
Exact meanings can be belied by a tone of voice, an artificially raised eyebrow or a smirk. But they are not unreal. Defined on linguistic competence, they underpin all aspects of human society, from agreements to buy or sell household commodies, to wedding vows, to treaties to bring an end to wars, to comedy and irony.
Conversation depends on the reality of exact meanings, with significance in pauses, invitations to say more, thoughtful ahs and ohs, waits for replies, avoiding interuptions.
The notion of communicative competence should not be allowed to get in the way of competence-based definitions of precise goals for treatment.