The problem seems to come from modern bolt-rigs with a heavy weight and a short hooklength, setting up a fast pendulum action as the fish is played. With each swing, the barbless hook can (allegedly) rock part-way out of its hold, then pierce new flesh as it rocks back in, creating a "tear along the dotted line" effect.
I'm not convinced, but I have little experience of bolt-rigs, so as I want to have a crack at a Cemex water myself, I'd better doctor some of my trout fly hooks. Rules is rules. But barbs can be made VERY small, and still do their job. Pity hookmakers don't seem to beieve it.