I don’t think he would have staged her death, or been concerned about the condition of her body, in any way.
I think his goal was to make sure she’d never be found, and time will tell if he succeeded.
I get the impression that the reason they believe she is dead, and the reason they believe she was killed in that house, is physical evidence.
This has to be forensic in nature, and I cannot imagine that it’s not blood evidence.
I can’t think of any other type of physical evidence, that would lend itself to this conclusion.