The angle of the reef clew line is critical to proper setting of the sail when reefed. This line has to provide the outhaul function, as well as keep the clew down on the boom for proper sail shape. If the clew lifts off the boom too much you might even run out of sheeting room on the mainsheet.
If the attached end of the clew reef line is slightly aft of the intended position of the "outhauled" reefed position, and the turning block on the other side of the boom is appropriately further aft of that point, you will get a downward pull and an aft pull to put the clew in the proper relationship to the boom and the rest of the sail. You lose some mechanical advantage, but pulling in the reef is still possible provided you don't try to do it with a load on the sail (also try to support the boom so you aren't lifting the boom at the same time)