I think there was a lot of vagueness about the SN. I wondered if the paed saying there could be 'genetic factors' was a bit of a fudge really, a nod to the parents (were we really sure that they could give an accurate account of their own childhoods, enough to know when they began to talk? it's very difficult for anyone to accurately date their own childhood development).
The fact that Toby's language developed so quickly in foster care suggests his developmental delay may largely have been due to environmental factors. I have certainly known chidren for whom this is the case.
There was a lot of noise upthread about the SW (and other profs') language, and lots of people saying 'why weren't they simpler' and 'why weren't they clearer'.
I have often noticed that it is very difficult to communicate clearly and effectively when you are intimidated (as anyone might be by Mike, who was clearly threatening) or when you are distressed/disturbed (as anyone might be by seeing the conditions Toby was living in), or when you are not being listened to, or when you are having to say something you find emotionally difficult. In those situations you have to try not to shout, not to let your own emotions get expressed in your words. One strategy is to be very formal and polite -- because you are defending yourself against your very natural desire to say something like 'clean the shit up and talk to your child you morons' and then run.
Although SW are trained in communications skills we have to remember they are human beings. How often have any of us come away from encounter thinking that if only we'd said something different it would all have gone better?