Yeah, sure ERD50, I know how you like to have references. I'm back from church, atoned for my swearing, so we can discuss further.
First: the blower delay is
absolutely essential for heating mode and should always be present. You are right about that! It is important for the health of the heat exchanger, and of course is important for efficiency.
Second: this delay, and
especially the fan speed must be matched to the tonnage of the unit. This is crucial, and perhaps what I might have slightly convoluted with the blower delay. All modern units have settings for speed based on cooling tonnage and heating BTU.
Even a properly sized unit that has too fast of a fan can reduce dehumidification. It is very important the installer get this correct. I wonder if OP had that looked into?
One other very oddball thing about de-humidification and blower delay is the design of the drip pan. Actual de-humidifiers drop into a bucket immediately out of the way of the air flow. Most HVAC units in the horizontal position have a large pan with drip water that lazily takes its way to find the exit. A vertical unit disposes of the condensate quicker. So I guess the problem is complex and really doesn't have a one-size-fits all solution. Vertical units may not even ever have the problem.
I did a bit of a search on stuff I found last summer when I was fixing my unit, and found that "blower off delay humidity" brings up some interesting conversations. Not everyone agrees, just as we don't here.
As for hard data, the only thing I could find this time is the Carrier marketing statement about this. It is marketing, so... take it as you see fit. I used to have this system which also included running the fan ultra-slow during humid events. It was kind of cool, but overkill. I found these modes would only rarely run only a few times per year.
Here's a pointer and quick quote to what I am talking about:
https://resource.carrierenterprise...._59tp6a100e21--20_article_1429461218267_en_ss