If you were to iron your seams open and kept a perfect SITD you wouldn't be actually quilting since you would just be going over the threads. But if you iron to one side you're stitching over the seam allowance. I like to iron to the side and the quilt very close to the ditch but not actually into the ditch. I find my wobbles don't show that way. They do if I try to keep in the ditch.