I have often pointed out that the very best hitters generate their exceptional power and bat speed with transfer mechanics that first accelerates the bat-head rearward to and through the lag position (bat sweeping past the catcher). With these mechanics, they have already generated considerable bat speed in the rearward portion of the swing plane before they direct their energy toward the ball.
The bat-head arcs through about 180 degrees from its launch position behind the head to contact. The bat first moves rearward 90 degrees to the "lag" position, and then 90 degrees from the lag position to contact. The reason the bat first moves rearward 90 degrees to the lag position is because a batter CANNOT generate maximum bat speed with a static bat at the lag position. Great hitters generate great bat speed because their mechanics is accelerating the bat-head around the entire 180 degrees.
Notably, most average hitters use upper-body mechanics that simply take his hands and knob toward the ball without first generating bat speed by taking the bat rearward toward the catcher. Driving the knob forward causes the bat-head to just lower and trail behind the hands.
Shawn stated many times in his analysis video that there is no rearward acceleration of the bat-head and that the bat only accelerated downward. Of course the bat lowers downward into the swing plane, but it also moves rearward. Shawn discounts (or misunderstands) the force applied by the top hand as the rear elbow lowers into the slot, even though video analysis clearly shows the bat moving rearward when this occurs.
There is no point in further discussing this with Shawn, but you be the judge: is there rearward acceleration of the bat?