You never know what you are going to get in a swap. I've been very disappointed too, so much that I really don't swap much anymore.
May I hone in to say... you should not be measuring your squares by laying them on a mat or a ruler... very inaccurate. They are only going to be accurately measured if you place a ruler on top of them, as you would when trimming. If you are swapping 6.5" squares, then you should own a 6.5" square ruler, so you can check and trim with it. If you are in a 12.5" block swap, you need to own a 12.5" square ruler. Always put the ruler on top to measure.