The new models started offering the new material in the 17 Flying Cloud models called "Landmark"; it was offered as an option along with the traditional "Gold Alchemy" which is the "slicker" material. It showed as an option in the FC brochure, but it was not offered in other models such as International, Serenity, or Classic line up. Not sure why they did that, but some FC units have it and some don't. The new interior is one of the reasons we are upgrading along with the ducted air, to a late model 2017, 28' FC Twin; we also did not like slip/sliding around on the cushions.
I notice in the new 18's brochure, that is all they offer is the new stuff. Likely had a bunch of that shiny slick stuff left so they did them at random to fill out the 17 line?