I know very little about obscure coffee as well.

I do know that coffee comes from East Africa / Ethiopia, and that there are many varieties there due to this.

Heirloom varieties tend to be more “wild”. Farmers growing in regions outside of Ethiopia tend to select stable varieties to match the region.

I don’t know about the frost protection from deep canyons, but it makes sense.

I opened a bag of freshly roasted heirloom beans from Jimma, Ethiopia this morning, and they were indeed more tart and fruity than the Colombian variety I had earlier in the week. The discussion tracked with my experience, at least.