I agree that UL has less safety margin but you also need to look at what level of safety margin is needed. Although thru-hikers are amazing, their "conditions" are different than mine. A thru-hiker is seldom alone, even if they solo. They keep bumping into each other. I have read of many cases where an UL thru-hiker starts getting hypothermia, and another hiker bumps into them and assists them. They cover the miles, so can camp "low", hike "high" not needing high altitude gear. They often come back to town or civilization every 3-4 days or so.

I hike alone, sometimes not seeing a single person for a week. I am mostly off trails. Nobody is going to bump into me and save my sorry behind. I have to be TOTALLY self sufficient. I camp "high" because that is why I am in the mountains! I do not hike 25 miles a day because I simply do not want to!

We can learn a lot from thru-hikers and I do like how the UL trend is making equipment manufacturers think on how to reduce weight in gear and develop new materials.

One way to save weight that has yet to be mentioned, is going in a group. Sharing group gear really helps. One first aid kit, one cook set, one tent, one GPS or PLB if you carry that stuff, one mulit-tool type knife, share fishing gear.