I recall years back that it was figured the hotter side (185*?) was more of a “flavoring” addition and the cooler end (155*?) was more of an “aroma” addition.
With that, at flameout, I add any sugars, honey, or extract (strong beers), and then place the wort chiller in. I’m not sure what temp I begin at as I’ve not cared to check (maybe I should), but I assume I’m around the 185* mark. I stir occasionally for 59 mins. I’ve not checked the end temp either (maybe I should).
As applescrap stated it seems when there’s a test conducted it’s hard to prove that anything worked convincingly. I’ve had in mind to test small batches comparing late addition times, whirlpools, and dry hops to see what I see.