I think, particularly for tablerunners/placemats it's a matter of the BATTING shrinking vs pre-washing the fabric. Unless it's 100% poly, it's going to shrink. More so, in my opinion, than the fabric is going to shrink. If you're using cotton batting, depending on if there is a scrim, you may be able to pre-shrink it, if that is your preference. I generally don't do the runners/placemats. I also have a roll of W&N batting that I use for my quilts because I LIKE the crinkly look in my quilts. But I still pre-wash my quilting fabrics. Probably a leftover from garment sewing decades ago, but also works for those funky/over-dyed fabrics that I seem to like for quilting.