Surely the verification is where the ball is going ? how it feels , the results that you get. There are many swings out there that will have so many different movements that a pro would say is wrong etc - but the ball goes into the area you want it to go.
Exactly my point. What happens if the ball doesn't go where you want it to. Is it the online technique, your interpretation or other flaws in the swing preventing it from doing so. How does the average golfer know? I have the most idiosynchratic swing on the forum with numerous flaws. However by getting lessons to suit MY swing I know where the club should be travelling and can deliver it there reasonably regularly. Without that intervention from the teaching pro, how would I know which of my flaws were in the way and which was down to the online video not being right, or indeed being perfect for me but not being able to implement it properly.
It is a simple concept as far as I'm concerned. There is a wealth of information and using it (as I have with chipping etc) is fine but I think (and it's only my opinion) that it needs to be done with trained eyes watching and professional advice to supplement this. I could learn everything I need to know to learn to drive from the internet, but would you be willing to travel in a car unless I had driving lessons and had passed my test