is anyone really advocating that a players should train to decelerate their stroke at or near contact?
I don't think this is correct if they are advocating decel.
I think take the racket to the ball and accel thru the contact and let it wrap to finish by the opposite shoulder or over the dominant shoulder for extreme top, late hits, or lobs.
But, I find decel on topspin strokes or serves to pretty much result in an error or a poor shot. I think start slow smooth, pull faster thru contact and continue to complete follow thru.
I have never practiced, been taught or observed good players decelerating at or immediately after contact.
So, maybe the racket heat slows due to ball impact. I can believe that due to impact and recoil of the stringbed. But, so what - start smooth and finish strong.