I'm doped to the eyeballs on cold medicine at the moment so I'm honestly having a hard time picturing the maneuver in question.
In a perfect world (in my head), a perfectly balanced square sail with the wind in it would remain square to the wind. When sailing though (unless on a dead run) there will always be more wind on the weather leech as the lee will be shadowed somewhat by the mast and standing rigging.
So, completely letting go of braces would swing the yards sharp up.
This can be seen when bracing about the (formerly backed) fore stack when completing a tack. In any sort of wind, as soon as the sail begins to fill it will want to keep spinning, crashing into the lee shrouds unless the new weather brace teams (assuming the fore is braced aft) keep control of it.
Again, as far as my bran is working today.