AS you can see the starting and ending line of the stitching are different. Hence the extra line of stitching to make the seam right. As you know if it isn't square when you get to the end you have whonky Log Cabin blocks. Which is ok if that is what you intent.
I want these square. I blamed it on using a different ruler to cut the strips, but it is me. Maybe I need to drink less coffee. LOL Chris