In this way, if there were no special encounters, the power of Outer-body Incarnation would no longer be able to develop. It would only serve as a backup plan to escape from the Golden Book of Fate. When the body and soul were about to perish, Outer-body Incarnation helped to retain a bit of Genuine Spirit and prevented it from being controlled. It was still unsure about how much combat capability it had.
Later on, people gradually discovered that this could be developed further using some special techniques, so as to cultivate some power in incarnation and turn it into a good source of self-help. However, it would be extremely hard to do that.
What kind of Dharma Laksana True Body you practiced depended largely on your cultivation method.