A little thread drift here but this reminds me of a captain who I flew with many years ago on the DC-9. When we would get above our descent profile (all in the noggin then - the 3 X Alt rule), he would SLOW from normal IAS of 280 to 250! (clean and idle thrust). Funny we always ended up even higher.
He had a theory that we discussed but I was relatively new to jets, he had plenty of experience and, most important, he was the captain so I just shook my head and watched the ensuing scramble to get down later. I often wondered if he ever got it.