I wonder if they could have been referring to using white on white for backing. Seems I read that somebody had done this and was ready to kill herself before getting it quilted as something in that process makes the fabric very sticky and it will not move smoothly..
Sure nuff, I was right. I just checked my Diane Gaudynski "Machine Quilting" book which states "caution, avoid white on white fabrics for the backing because they do not move freely over the bed of the machine and will cause jerky, uneven stitches."