why would Hook be hitting himself? Hook should still be in neverland now!
They’ve never confirmed before exactly when Hook left NL and returned to FTL before the Curse. So they could put him back in FTL at the time of Snow Falls and not contradict anything they’ve shown previously.
We’re going to be told how Hook got to our world after the 3B Curse, so assuming that has something to do with the JR, it could explain why they’re on the ship in the finale, trying to find a way to get back. Dunno that a thing that could make regular world jumping possible could also make time jumping possible though, so whatever idea they have by going to the ship may not work. Anyway, it would at least explain why they’re there so Hook can punch himself.