The only Jones Act employees in this hypothetical we're talking about (because they didn't have a skiff) would be those that actually "crew" the skiff . . . as opposed to some non-vessel worker that gets assigned to the be construction contact on the skiff that limited period of time (though that could be subject to argument depending on the length of time that person is assigned those duties). There's all sorts of intersting case law on seaman status.
But there wasn't a skiff here and if there was, there's no reason to think anyone on it would have been injured or killed.