Garry, the photos show my blue 1966 230SL, my current 1964 230SL has leather from the factory and I don't intend to change that.
Anyway, yes when you press the top part next to the wood it is hard but I believe that there is no foam left to speak off, just dust.
I encountered the same on the folding top compartment lid. It was hard to the touch because the foam underneath the vinyl was in crumbles.