I am not in the least surprised to hear (read) the rumour of some Boeings and for a very simple reason.
For many, many years, SAA was a Boeing 'house' and there are many still there that mourn the change to Airbus (IGNORING any technical reasons) and so any chance to get an aerie that starts with '7' will be tried.
Had SAA have been a McDonnell-Douglas 'house' they would have been equally upset at the change. It is the change not the direction of the change. For others, of course, it is the direction but the unfamiliarity of a new everything, leaves people wanting what they had before. It's entirely normal. BUT, having made one big switch - SAA cannot afford to make another. For better or worse, stay with aeries that start with '3'.