I did find this from the Boundary Waters Journal in 2007 when the barbless ban for Quetico was being enacted.
“Reilly (Quetico ranger) is aware most studies show little significant difference in mortality rates between fish caught/released with barbed vs. barbless hooks, but he believes in actual practice a worthwhile benefit for going barbless can still be found. That is because over one third of all Quetico visitors are youth groups of novice anglers who dabble in casual attempts to catch a fish dinner.”
and
“Reilly gets satellite phone calls from groups with some kid impaled by a hook on a remote interior lake requesting an aircraft evacuation. Of course, this brings disruption to other nearby campers. Barbless hooks will be easier to backout of humans, making such evacuations less necessary. This is a secondary benefit to banning barbed hooks.”
So at the time they called it a “secondary benefit” while admitting that the research did not support their logic for the “primary benefit,” which was to reduce hooking mortality. A guy can read between the lines to infer that reducing costly air evacuations has actually been the most significant effect of this ban, and another ranger said as much to my friend in conversation.