" I noticed many shell off restorations, that people are slathering on a black sealant inside the exterior panels, covering all of the seams and rivets. is this just Trempro?"
I don't think there's a black trempro.
The black sealant I used was a black polyurethane roofing sealant. I put good amounts, huge beads, on the seams and rivet backs with a caulk gun then spread it around and forced it into everything with a rubber gloved hand.
This is the stuff I used, Amazon description isn't great.