I had to think about that for a minute. You either keep the loaded side cleated or, when the traveler moves to leeward, you have to pull the line through the leeward side.
Better than nothing, I suppose. Not sure I love the idea of a line being taken up off the deck, without intention. If ever there was a time for an accidental jibe, it would be on a run in the dark.
However, for that reason, I just wouldn't be on one without tying off the boom. Or, if I was concerned about the sea state and going forward to tie/untie, I would fly just the foresail or bear up and avoid the doom.