@goatsarah the leading & fringe theories do seem to share the notion that however it started, the teenagers are doing it for fun, as a fad. I'll admit I thought it was funny for a moment when I first heard about it - but like you I then remembered that if humans start to think orcas are dangerous, that's gonna be nothing but bad for orcas, maybe everywhere.
& between this story & the increasing observation of 'shark hunts' ordinary people are beginning to remember orcas are apex predators.