I found the block and technique in this book. The blocks get trimmed to size after sewing which works well when you have a lot of different people making the blocks.
I haven't trimmed the sections for the second block but I wanted to show that you get both red and blue pinwheels when the blocks go together. I think this is similar to the little twister blocks that you cut out of a large piece of patchwork with a template. The edge of these blocks are on the straight of grain.