Called and few more dealers and spoke to someone who didn't mind taking the time to discuss. Apparently there are two body styles on 2019-2021 and possibly 2022. Classic and new. Classic is the same as the older and a topper that fits the older should fit the classic style trucks. I talked to the dealer about our new truck and he supported the info by stating he went through the same deal with his truck.
Yep, the 2019-21(22 if they make it) classics are just a continuation of the 4th gen that has been in production since the model year 2009. The 4th gen is know as the DS platform, so that would include 2009-18 and 2019-21 classics, the DT is the new style 5th generation with it's first model year being 2019. Making both trucks concurrently leads to a lot of confusion for parts ordering.
The HDs are also still using the body/cab (other than new front end) from the 4th gens, so a lot of parts could fit for people looking to swap over HD parts from something older.