While I do agree that with an injury like this the body is in complete shock mode, I feel like I've seen other person-cut-in-half videos where the person was still alive and seemed to be at least partially aware of what was happening, who was around them, etc. One where a teenage girl was cut in half by being run over by a large truck and her mother was at her side and if I remember correctly it really looked like she was talking with her mother. But I might be misremembering... I'll have to find the video again.