Actually the Buddha and some of our enlightened monks know alot more than the existing sutras but are not willing to say further. Maybe we have lost some sutras or maybe they are worried some of us might use part of their knowledge to create mayhem. This is just an example, let's say the Buddha dismantled the entire machine to show us how things work, and part of the machine has a certain centrifuge and one of the students use the centrifuge to create a deadly weapon. The Buddha may get entangled in some ways if the above happened. Many angels (天人/仙/龙) got adversely entangled through this way. In my opinion, if we diligently practice the existing sutras and if we can engage a good master, we will reap good results.