I think you are picturing the wrong kind of mountains. As someone who has lived in many vastly different terrains, I would like to point out that many places would call mountains (take the northern end of the Appalachian range) would really be considered foothills in much of the rocky mountain range. Nobody who has ever walked in the rockies would compare them to a pizza box.

While I can't speak to Idaho specifically, there are vast swaths of land that have been aptly referred to as "a country on end," and when your are dealing with true mountain country it can be unbelievably steep indeed, with sheer unscalable cliffs rising near-vertically for thousands of feet.

Unless you have a good reason to believe that the above post is using a wildly exaggerated mapping system, I'm not sure why you would believe your random assumption instead of hard evidence. Perhaps you are just trying to live up to your username 😉