I think one of the most important phrases in debriefs is 'In that particular situation....'
I get completely, that to teach 'grey' from the outset is difficult, and that to dish out a set of rules is a lot easier.
'Move away from a nearside junction as you approach it'. 'Give oncoming traffic a wide berth and move to the nearside as they approach you'. 'Deal with the junction on your nearside before the right hand bend'.
If I took up something Ive never done before (I often use the analogy of skiing), I too would want my instructor to say 'do this' rather than 'well you could do this, or you could do that .. what do you think?'. And so it is that we generate the rules, the black and whites, the chess moves, the dot to dot riding and the dreaded paint by numbers style.
The best debriefs and teaching styles should break down the ride and get the student to see why on one occasion he might do X, but why on another, almost identical scenario, he might do Y.
A Janet and John example would be a nearside junction prior to a right hand bend. In one scenario where you can't see into the junction and it has the classic high hedgerows etc etc then Yes, you'd expect the student to open up his view before dismissing it and then positioning for the bend.
But you might have an almost identical road layout 10 minutes later, the only difference being you can clearly see into the junction and its completely empty. The thinking rider will see its no threat and will position for the bend early, sailing over the mouth of the junction in the process.
That sort of stuff is pretty elementary, but a good debrief will be 'In that situation .....blah blah blah ..... but can you see how in that very similar scenario that you had ten minutes later you can treat it differently because .... '.
We don't want chess moves! WE HATE CHESS MOVES !!!! We want thinking riders!
Moving up the league table of Janet and John scenarios we eventually get to what sorts good riders form great riders. And great riders have a wonderful touch about them. Wonderful acceleration sense, they can dance with the road and the traffic and make it look so easy. They see the little opportunities to ease up and let something develop in front without ploughing in themselves, little opportunities to have a squirt of gas and pick out something from nothing, great restraint that can go hand in hand with an amazing turn of speed. They have .... 'touch'. Whilst I accept that they have developed that from a foundation of core principles and dare I say it 'rules', what you won't see in them is riding by 'rote'.
