I walked a few miles in flip-flops and the top part started chafing the top of my feet. I don’t see how he can walk thousands of miles in them
We were on a 45 mile backpack trail and came across three Canadian college students who were woefully unprepared for such a trek. Among other things, one has only a pair of flip flops instead of proper hiking boots. Within two days, he was getting aspirin from everyone he saw on the trail due to shin splints. To their credit, they completed the trail.