Component #20 is the RELEASE Trigger, NOT the "downstroke trigger". Accordingly, the five Variations in 10-20 are the five procedures available for triggering the Release of the Power Package, NOT "5 ways to start the club down".
There is no such animal in The Golfing Machine as the "downstroke trigger". Stating otherwise is just plain wrong. And on this point in his Authorized Instructor training, Homer Kelley was adamant:
"Explain the terminology any way you want. But . . . don't replace it!"
Or, I might add, confuse it.
I think we need to stop confusing the Tommy videos with the facts.
If I re-watch Tommy's Chapt. 2 & 5, maybe the facts will fade away.