I can't think that it would matter in what order you quote the co-ordinates for a shape, so long as each co-ordinate is written in the correct way (x,y). It would be neat to quote them all in clockwise or anti-clockwise order but I don't think it could ever really matter could it?
It depends if the co-ordinates are defined as the corners of a shape (in which case the order doesn't matter) or there's an implication that you can draw from one to the next to form the shape. (0, 0), (0, 1), (1, 1), (1, 0) are the corners of a unit square, and if you draw from one to the next, and then back to where you started, you've drawn a square. (0, 0), (0, 1), (1, 0), (1, 1) are also the corners of a unit square, but if you connect the points in that order and then return to where you started, you'll have a bow-tie shape consisting of two triangles.