I began to wonder if it might be the difference between bias binding or straight cut but maybe not after reading previous comments here. Mine is cut width of fabric and I don't press because I think the binding loses a few threads in the turning over the edge and, besides that, it's just one more step that I find unnecessary. This is another of those--whatever works best for you tips! Whichever way you do it, nobody will know when the quilt is finished.