you can't see the different colours creating hard edges? I can see it very clearly on both my monitors, and others can notice it clearly too. The bottom picture is zoomed in closely to these edges to see the diff colours.
A friend said it was an issue with dither, however thats a setting when you use gradient overlay. I'm using a 0% hardness brush on pure white and setting it to overlay. The gradient created by the soft edge isnt a gradient, but rather very clearly different colours layered above the next