I guess it's because he really isn't, on some level, in control of it. He doesn't forget it happened, but he can't necessarily recall what it's about. Or maybe he doesn't want to on some level.
Right now I realise I feel so stressed at attempting to help DS with English that I end up not doing it. Not because I can't bear the thought that DS won't pass English, but I can't cope with the thought of DH not coping with it.
I realise I have a mindset that is very 'There is always a solution, there is always a way through, even if things don't go to plan', most of the time. I may worry about something, but I essentially believe there's a solution and that's the same with DS and English. OK, worst case scenario he'll have to take Functional Skills and move on, and my view is even if his GCSEs aren't stellar he has a lot of social advantages compared to many people that will help him.
DH I think is much more catastrophising about things. So this kind of mismatch makes it hard for him to understand that I am trying to be reassuring about 'Plan B', as in trying to say 'There's no need to be frantic, there is a solution that is good enough to progress if it comes to it'; I am not saying 'Let's not bother to set our standards any higher'