I checked with my friend. apparently she wasnt allocated a CO too. She came to Australia on 475 as a dependant and when it came to the 887 visa application, she applied as the Primary. She didnt submit a form 80 and 1221 and resume. She also didnt have any non accompanying dependants.
You might have to check with someone who included non accompanying dependents because my understanding is majority of us didnt include them. Even though they are not accompanmying you at this time, there maybe a possibility that they might join you at some stage and for that reason DIBP may need all their details too. Atleast that what i think.
It will be best to check with someone who has included them in an application