A question on MN 39 Mahā- Assapura Sutta

The Buddha in this sutta describes the gradual training of a Bhikkhu step by step. I have a difficulty understanding some of the steps in precise detail because of the statement at the end of most of the steps pescribed: 'Bhikkhus I inform you, I declare to you: you who seek the recluse status, do not fall short of the goal of recluseship while there is more to be done'. I am not sure how the step of purifying conduct and livelihood in the way he describes it does not the imply restraint of the senses from all the way up to the abandoning of the hinderances i.e how can one do it without doing the rest? Same with restraint of the senses until the abandoning of the hinderances and mindfulness and full awareness until the latter. So Why is it then that in these three steps one is not cultivating any of the other steps subsequent to it?