I think this has been shown to be mythology as the difference in tension in an uncocked spring compared with a cocked spring is very small. i.e. in an uncocked state the spring is still in tension, probably around 80% of the cocked tension, in order to get a more linear response. If the spring went slack at the end of the movement there would be a huge difference in tension across the travel of the shutter resulting in it slowing down towards the end of its travel.
Originally Posted by PentaxBronica