I'm making 10 minute blocks right now, and have made many (at least 2 other whole quilts) before. I couldn't figure out what you mean. I looked at the back of mine, and I don't have any abnormal bulk, so I'm not sure what is different for you.
EDIT: In the above photo it looks like the center seam is all twisted. I make sure that my seams are pressed and all going in the appropriate direction. Maybe that is the difference.