If teachers don't usually instruct in the direct way, the reason is either that they don't think people will understand it or they don't know it.
Agree. Teaching should fit the student.
In either case it shows that the direct method is for those who are already well prepared.
What do you mean by well prepared? What if you apply a low teaching to a "prepared" student? What if you tell one who is ready for direct teaching, to go and do something contrary? Teaching is chosen for students, but as we are not teachers here, we should talk about how things are, not about how teachings should look for some particular group of recipients.
Rinzai Zen (Japanese) has a clear systematic training programme that actually culminates in the contemplation of the bodhisattva precepts.
And how different it is from the founders (Linji) approach...