[EdZ]

What do you see(or know) as the major culprit for people that have a BACKSWING BOB(SPINE ANGLE GETTING MORE VERTICAL)? Bad back, tight hamstrings, visual, other?

Lack of flexibility a fair amount of the time.

Most folks aren't flexible enough to take a club back to 'top', let alone to 'end', without disrupting alginments.

Show them proper extensor action and they'll see their flexibility limit fairly quickly.

Left shoulder 'under' the chin is a helpful visiual for folks that tend to do this IMO, as is letting the left foot come up on the backswing ala Jack.