I agree. The reason it works is because when you pull the bat back, you often pull everything else back against the rear leg. When you turn the barrel, the rear leg pulls. It's a good way to get the feeling.
Based on Your HI level experience correct ?? Or what You have read?
When I see the 'showing the bat' & 'pulling the bat back' I keep thinking that some how this could/would tie into the BB/A$$.
The 'showing the bat' & 'pulling the bat back' to me 'sets/starts' a hitter with the BB/A$$. It also is a way for a hitter to pull back and get 'over' the top of the rear leg instead of pulled back against the rear leg. I also see when done correctly a way for a hitter to get a 'running start'. If nothing else it seems to get the hitter into the proper hand set. JMHO.