I agree. Which, again, makes me wonder if it really did happen in that bathroom. It suits SH for it to have been done in there with the door locked for 3 days. Any other room and it would be very hard to come up with a reasonable explanation as to why she was kept out of a room for that long, or how she could have avoided seeing anything.
I can't shake the feeling that NM is telling a story which is deliberately full of lies - that he knows they can prove can't have happened that way. I can't explain what I mean very well - but he has admitted to killing Becky, but everything he describes isn't actually what happened. None of it makes sense - the kidnap story, SH not seeing a thing, telling the police he dismembered Becky in a room that he knows has no evidence in it whatsoever.
I think he is giving them such a bizarre story to completely cover up what really happened and perhaps where it really happened ..... but I don't know why. Could what happened be even worse than what we know? To protect SH? But would a violent, bullying, controlling partner, who has displayed that sort of behaviour for so many years, suddenly find his conscience and immediately revert to being totally protective and do all he can to protect the person he previously controlled.
I don't know very much about domestic abuse and that type of control, but I've read a lot of cases where the man doesn't change the behaviour, despite court rulings and even prison, and continues the abuse and the behaviour. NM seems to have 'reformed' immediately.