Since this thread is several years old, I am surprised that no one (including me) responded to Bruce's post. No, the plywood / fiberboard (TM has used both over the years) is not glued directly to the foam. As you know, the walls consist of a layer of foam, with an aluminum skin bonded onto both the inside and outside surfaces of the foam. As you noted, the skin on the inside surface covers the entire wall, and the plywood / fiberboard is glued to the skin.
Our member Larryjb addressed the same issue a year later, with a picture of the layers. Check out his posts in the thread at
https://www.trailmanorowners.com/for...ad.php?t=18922
It will answer some of your questions, I think.
Thanks for noting the correction. A Search for "wall board" (without the quotes) should bring up more info, as this has been discussed before.
Bill