THANK YOU. you expressed that much better than i did. and i'm glad (well, not really GLAD!) that someone else has had that experience so no one thinks i'm crazy. and i have had that experience with some of the top manufacturers, so i know it's not just cheap fabric.
i also finish off the edges, whichever way i feel like at the moment. sometimes zigzag, sometimes i sew the edges together. i wash in the hottest water to get all shrinkage and grain twisting over with at once, and dry in the hottest dry cycle. same reason. as soon as it comes out, i lay it flat and hand-press. i trim the overhanging edges and throw any usable inches in my scrap box. no matter how off-grain it now is, it's finished. it will never get worse. when i sew, i starch or size, so the edges, which are now slightly biased, are no problem whatsoever. so i just cut my fabric and sew. with this technique, i have never had a problem.