In a 1981 GSEM Class discussion, Homer Kelley referred to two types of Clubshaft Bend for Swingers. The first -- "Acceleration Bend" -- stresses the top of the Shaft during the Start Down. During the second -- "Release Bend" -- the stress is opposite the Acceleration Bend as the toe of the Club attempts to get in line with the #3 Pressure Point.
The Hitter's stress is at the back of the Shaft and does not vary.
It's interesting that he mentioned both of these bending features because some of the guys doing advanced shaft fitting take into account the bending characteristics at different points (zones) in the shaft. Specifically, the swing tempo may be considered for "Acceleration Bend" (using your terminology) and release quality for "Release Bend".
As I mentioned earlier the "Release Bend" is generally toward the target for almost all golfers (for full swings) and is caused by the centrifugal force due to the clubhead speed pulling outward on the shaft through it's center of gravity - thus, CoG wants to line up with the shaft axis bending the shaft forward. That's why offset heads tend to hit the ball higher and could slightly correct a fade because the CofG is further behind the shaft and the shaft will tend to bend more forward with these heads. Ok - maybe too much information there.
Still a little dubious on the impact deceleration concept - but it may be a "real vs feel" thing in that it helps to think about accelerating through impact to avoid quitting, throwaway, etc.
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