Very well explained cabbagepatchkid. When I sew a scant 1/4" I am sewing less the thread thickness which is about 1/32. In my opinion this started as people did less pressing in their block constructions. In the past we had that thread in the seam taking up space but we still sewed 1/4" but we pressed seams at each stage of the construction. I had an excellent teacher and friend who taught me proper pressing and I have had some good chuckles when other describe how they press.