I'm reading between the lines here.
In Henri's statement it strikes me as odd that he was at pains to point out (more than once from memory, I haven't listened to it again) that he heard Rudi making gurgling sounds. So Henri is finding a way of explaining something - Rudi had survived the attack, like Marli. This makes me think he is compensating for a finding of some sort, and I expect it will be that a further injury was inflicted after the main assault. Perhaps one injury didn't bleed out as much as the other injuries, because there was a weaker pulse by that time.
Henri can't get around that by saying Rudi didn't die straight away. I think it's going to be very interesting and if I'm right there will be much arguing to come over Dr Anthony's findings.
I'm also wondering if, because of Marli's condition and the immediate surgery she required, they weren't able to do the same sort of examination on her injuries, but that they would have shown something similar, a later assault on her jugular vein, and that is why she survived the 4 hours. It's possible that because she was lying so close to her mum that Henri couldn't get to Marli without very obviously disturbing the crime scene with foot prints he wouldn't be able to clean up.