Actually, both views are correct. Regardlesss of how the phase difference is generated, if you view the two legs of a 240V service on an oscilloscope the two voltages are in fact 180deg out of phase with each other. Note that the post that generated the discussion did not even call it a two phase system. It only said the two voltages in a 240V service are 180 deg out of phase with each other. That is correct. If they showed that picture on a EE test and asked "What is the phase difference between the two signals, what would you answer have been?"