does it matter than there isn’t a threat as long as you genuinely believe there is?
I think this is true, but I'm not a lawyer, and not a South African.
The thing is though, I think he'd be hard pressed to claim he thought he was in genuine, life threatening danger, seeing as he didn't see an intruder at all, let alone see whether they were armed, and there was a door between them, and he could have shouted 'I'm armed - I'm calling the police; stay where you are or I'll shoot you'.
I remember his answer from the gun licence questionnaire - Are you allowed to shoot an intruder who is stealing your television - to which he'd answered 'no; there is no clear danger to yourself.'
I'm guessing, from that, that you're not allowed to shoot simply because someone was an intruder. You'd have to have an honest belief that they were armed, and were intending to harm you.