2019 Silverado Tow Mirror Install

[eng413ine]

 New to the forum, first post. Looking for a little help. 

I just installed the tow/camper mirrors on my 2019 Silverado RST. I also installed new harnesses in the truck. The truck came with DLF mirrors and PEPS. New door harnesses are 84622371 and 84622372. Right after install the following worked on the new mirrors: mirror adjust, mirror heat, temp sensor, and driver's side only clearance lamp. What is not working on the new mirrors: passenger side clearance lamp, turn signal lamps, and cargo lamps. In knew the BCM would need to be updated, so I went to the dealer today with my code and they said the BCM cannot be updated because the truck doesn't have right hardware (connection to BCM?) to make the non-working features work. They couldn't explain why clearance lamp was working on one side, but not the other.

Questions: Is what the dealer said accurate? Is there an add/update available for the hardware to make the features work such as an aftermarket connection kit?