FYI you are correct about that warming period being in medieval times. I thought it was, but hadn't read it in a long time and wasn't sure. I don't remember details over time, but the general idea. So I took it out because I didn't have time to check it. I also had seen the counter argument from your side on it before too.
Bill Belichick learned to film signals of opponents from the former Chiefs, and Charger's coach Schottenheimer. Others like Edwards, Johnson and Cowher did too. They learned from the CHEATS and CHEATERS who still couldn't win.