Why would you place potatoes on salt when baking in the oven?

Several of my recipe books call for baking potatoes on a layer of (rock) salt , e.g. I'm currently following one for gnocchi that has this very instruction.

Searching yields many recipes , but I can't really find the "why" of it, nor what it technically accomplishes. Our own cooking.se site yields no relevant results either.

I can't quite imagine either what it would accomplish, except for perhaps salt the potatoes a bit; but that seems rather inefficient (why not add some salt later to the gnocchi dough?). Or perhaps it's meant to draw all fluids?

Why would you bake potatoes on a layer of (rock) salt? What does that do to the potatoes?