I can vouch for the fact that this actually happens. I was making a quilt once and sewed top to bottom about 20 strips. About at number 10 the bottom half started turning right. Could not get that thing to straighten out. Had to rip the entire thing out. Definitely sew top to bottom, then bottom to top (flip it around). No problems after I started doing it this way. Go figure! But's definitely true. Usually I could tell which direction I sewed next because the end I started with was always perfectly flush (the two pieces) the "finishing" end was always just a tiny bit off.