Here quote from the SAC handbook, a copyrighted document, I plead fair use to further discussion on relevant issues, translation from German and oblique explanation by me:
The SAC hiking scale, introduced in 2002 and last revised in 2022, enables a graded assessment of the difficulty of hiking routes. It ranges from T1 to T6 and takes the following aspects into account:
- Difficulty of the terrain («technical» difficulty)
- Exposure («mental» difficulty)
- Difficulty of orientation/wayfinding
- Risk of deep falls (below walking ground)
Generally, the scale is not about hazards, it is about difficulty only. So why deep falls? Because those are the physical base for the mental thrill called exposure.
Path well cleared; terrain not level, if not steep; no sure-footedness required.
PS: The take the SAC has on term exposure did remind me of how the term is used in the U.S:
I remember having read in this forum someone from Australia linking exposure to sunlight. That reminds me of the full name of mine here, ASA 100. I still think “head for heights” means, not having the feeling, or at least not getting crag-fast from it? (Another English term I like a lot.)