This is it. They price installs at generally a single day for complete system swap for install time assuming ducts are reused and never want even spend the travel time coming back on another day in my area. If they do, it’s eroding the profit they expected on your job. They usually have special crews that only do installs and also generally like to keep to a small list of manufacturers so they can keep as quick and efficient as possible. New and unfamiliar tech throws a wrench in that.