of the screams was that they were not sure they were hearing M's voice.
Whereas Z's uncle was convinced he was hearing Z the first time he heard the cries.
I once read a book about how first impressions are often more reliable than considered opinions. It's called Blink.
It makes no sense that someone beating the hell out of someone would be crying for help.
Unless they had a manipulative kind of mind. But I don't read M that way.