you must understand pro players view this stuff very differently to most of us. dima has been backhand flicking since he was 7 years old, his level of automatization is so high that he probably has no idea about most of the things going on in his stroke. when he explains the stroke he is actually just telling us about the stuff that HE thinks about when performing it and everything that he doesn't have to think about is lost in translation.
what is the contact point on the ball for different types of incoming balls?
what is the contact point on the bat for different types of incoming balls?
what is the angle of the stroke in relation to the angle of the bat?
what is the position of the wrist in relation to the forearm at the moment of contact?
what is the position of the forearm in relation to the upper arm at the moment of contact?
when dealing with short heavy back spin balls, since the table prevents a downward back swing how much of it is to the back and how much to the side?
how loose is the grip on the bat, at what moment does it tighten and how much?
i'm sure one could think of a lot more questions... in general, the worse a player is at a certain stroke the better questions they have about it and the higher the chance that they successfully break it down and understand it on a theoretical level. most pros would just tell you "well, you come in with your right foot like this and you put your hand like this and then you go forward like this... for under spin go more from underneath, for top spin go more over the ball and voila".
You are right. I just want to add a few points:
BH flick is not the same for everyone. Ovtcharov does it differently, ZJK does it differently, FZD, ML, etc. all of them do it a bit differently from each other. Same question, Ovtcharov's answer will be different from ZJK's answer, Ma Long's answer, etc.
There are so many variations and factors: grip, short/long flick, fast/slow, spinny/less spinny, side spin/top spin, spin of incoming ball (combination of top/under spin and sidespin/reverse sidespin), flick from BH/FH side of the table, flick down the line or cross court, etc. Too many factors and no one can teach all of these in a video. Most likely they give us the principles and some tips and we need to experiment to find what works for each of us.
I think Ovtcharov gives us a very nice tip in this video which is the part about the body and elbow position to have more space to accelerate the stroke. I also believe the grip is very important in this stroke, some certain kinds of grip will allow us to add more spin/speed.