Welcome aboard Sodo. The video you are refering to is this one I think: https://www.youtube.com/watch?v=ExasOaC92f4&feature=share&list=UUn9et-2QPY1vkb7DOe8Xtgw
Ive been doing judo since I was six, so obviously my way of teaching has been very much influenced by judo. I dont think there is need for explanation how and why. Of course Ive been doing a lot of other sports as well and theyve changed my view on grappling a bit. But going through all the layers of the grappling arts, I found many similarities. There are layers of complexity, at first there is basic body movement, then there is the basic principles of positions, then there is using those principles to apply techniques against a compliant uke, then there is the situational drill where we put the techniques into a context, then the randori and finally the competition.
Its very easy to go straight to the third layer and just show a bunch of techniques and then let the guys randori and see if they can use it. This is in my opinion wrong. The technique I show is preceded by many hours of doing ebis and studying the mount position. The reason I made this video was to show an opening to sequence a few techniques on. By pushing on the arm there is going to be a reaction (based on the body movement of uke and the pricinples of defense).
Usually after showing a series like this, and having the guys train this for a while, I let them do it against a resisting uke by creating a situational drill. A kind of randori but with very specific rules. For instance, the guy on top has to submitt the guy on bottom, the guy on bottom can only defend, not counter. By doing this the guys get the most effeciency out of using the newly learnt techniques.
In judo I really loved the structure of the classes and the way techniques are slowly transformed into useful pieces against resisting opponents. So randori and competition being in generally quite chaotic, by applying certain techniques and creating reflexes, you can go into a more regulated state of fighting. I dont believe in learning tricks against unresisting ukes and going straight into the most complex layers of grappling. I believe in simple openings, where techniques will flow from automatically, based on muscle memory and principle movements.
Does this answer any of your questions?