The discussion is should you do nothing until you visually acquire the traffic because of the inherent errors in range and bearing accuracy and because the other pilot might resolve the conflict in the same but opposite way to you.
If my PCAS is showing a contact closing steady at the same alt I may change my alt to avoid. If above and coming down I'll make a judgement as to what to do depending on the rate in change of height and difference in height. Doing nothing does not make much sence to me.