It is an optical illusion. All the blocks are the same, a wide fabric and two borders that equal the length of the block.
So an 8" finished square could have a six inch finished piece (cut 6 1/2 x 8 1/2) with a 1 inch finished border on each size. They would be cut 1 1/2 by 8 1/2 inches. One block is sew with the borders horizontal and the next with the borders vertical
When you do math, you use the finished size of the block and add the seam allowance. This is a great pattern for a print that just has large printed stripes sometimes called a wallpaper print.
I had to scan in a photo of my Mother in laws quilt. The close up is of the block. The block is a stripe cut horizontally. It is one piece of fabric for the block. You can see part of the stripes of the vertical blocks next to it. So I cut the block as wide as the center motif plus the two borders printed next to it plus seam allowance. It sure looks like I worked hard, but didn't.