I guess some people downvoted me because they took "Medieval" to be pejorative. I was being entirely literal. Linen-based paper was widespread in medieval Europe after the plagues. (Much of it was made of the linen clothing of people who no longer needed it, on account of their being suddenly dead.) Such paper is much more amenable to folding in the manner of a map than earlier technologies. (Though most everything seems to roll up into scrolls well enough.)

Scrolling and zooming are not appropriate substitutes for folding in electronic displays.

That's entirely contextual, as you also point out. You won't know how well things can take folding and how well the form factor performs in real life until you have such materials. Until then, we know zooming works. If I had something as light as and the same size as a clipboard that was daylight readable and yet as dynamic as an iPad, this would enable a whole other world of mobile applications that aren't quite there yet. I'm hard pressed to imagine an application I'd need that could fold out, which couldn't also be met by presentation/projection systems, or perhaps an interactive worktable form factor.