That was utter horseshit. I am absolutely certain I was correct to select detective for the winner to begin with and that a team that always cooperates will convince the copycats to get rid of the cheaters in real life and convert the remaining copycats into cooperators.
I know I chose right: Detective wins in 1vall but always cooperate wins in teamfight because always cheat gets ganged upon soon enough and all others convert into cooperators unless they are stubborn grudgers in which case the copycats and detectives handle them. The detectives are blackmailed into taming and everyone becomes 'always cooperate'.
Copycats don't win in life, you can easily outsmart them as a detective player, I don't know what on earth that thing tried to prove.