I'm making a wild guess JG and EC thought 8 miles was a "short stroll", and that's why they were provisioned for a short stroll. This would explain a lot.
PS IMO Under no conditions is 8 miles a "short stroll", except maybe on your calculator when you insert a pace of 3.5 miles an hour with no breaks. In reality, it's not a stroll at all. And in those conditions, with that preparation, it's a death march.
Maybe
@MrsEmmaPeel could check? Does that mapping app they used let a person calculate how long it would take to do that loop? For instance, could they have plugged in a pace and have the app give them a completion time? That could have put them wildly off, and magically turned a major hike into a "short stroll".