Why-man could be a robot or generations of why-man or it just what you said since they didn't do anything to Rei when she's so close to the moon. We don't know
Well, this is my own opinion but if senku's theory about the medusa device can make a dead person alive or somehow immortal is true then it's either whyman is on brink of death then turn himself into stone,cameback, and watch over the earth for thousand years since after petrification they can't die from old age but they still can die if someone kill them since whyman illustration shows skull like thing then that might be the clue that a human body will still rot but still somehow alive with the help of medusa device
Ok im curious it has been thousand of years now that they revived. If the why man is on moon are you sure he's not dead or he's really there? Because no matter how slow the time outside earth progress or time dilation, thousands of years can be said too much and statistically speaking, the average age of death of a man is 80. I think there's just some loop triggering this Morse communication from earth to moon vice versa, and why man is actually on earth, stone like others.