Discussions about stroke- no matter what style talk about can be really fun, informative, and depending on the reason of the discussion very helpful.
ONce a person joins the discussion, which would be lookin for the holy gral....the discussion is worthless- ending in flame war.
once a person joins the discussion who just want to state what is right an wrong....same type of worthless discussion.
If I have someone, who just begins too play pool-- i try to explain, what the goal is (of a stroke). What can be helpful to make it much more repeatable-
The physically given things (height, is he sporty, age etc) are also very important!
Just because I am one of those "SPF" Instructors does not mean, that i would teach it nonstop all the time. (the pendulum stroke).
And I am 100% sure, that every other qualified and expirienced instructor is on the same line.
If you have someone, who is able to deliver a repeatable straight stroke- which allows him to HIT CUEBALL where he wants to---and furthermore is able to send it from A to B (where he wants it to go of course, lol).....then you should find no instructor, who would try to fix it. Never!
Textbook Stroke? Maybe a hand full in the pro circus.
No matter if you teach someone a Pendulum stroke, a Piston Stroke-- or a mix of it (what is in my opinion the most found outthere)-- what an important point and job is:
To find HIS PERSONAL SWEET SPOT- which needs a perfect physical setup based on his physical given abilites-- to put every part of his body which matters in the right position.....to give him the best opportunity to deliver a repeatable straight stroke.
Key is: the player has to understand, that he MUST be able to deliver the cue as straight as possible-- and find his way to achieve that. And to do this on your own is terrible difficult.
a smooth and straight stroke to everyone