I think you can need to be surefooted on unexposed terrain (say hopping along talus or boulders on a dry stream bed). I’d rate that as PG.
surefooted and with a head for heights / composure would be more R - X exposure. I just whipped up this real quick to go with my previous hiking_technique key. I had it mostly written for another project and just had to swap some phrasing around. 
At some point soon I’ll try and get a us_trail_visibilty and then the three can be put together and see how effective / accurate they’d probably be,