i'm not 100% sure, but it seems that it would torture the fish before killing it slowly. it would be easier to get it over quickly, because if someone tried freezing the fish, it meas that that they probably cared for the fish and don't want to let it go so easy. they would check on the fish every few minutes, and they would suffer slowly too, though not like the fish. like i said, i'm not sure if what i said is true, but it makes sense to me.
there's a difference between a freshwater and a marine hatchet-fish. one looks cool, the other gives you nightmares.