If you look at the picture, here,
http://materialgirlquilts.wordpress....e-sampler-qal/ you can see the sashing is definitely not 5 inches each row. Plus if you do the math, the finished quilt is 79.5 square. Four 16" blocks are 64", so 5" sashing would add at least 25".
I've never done a BOM, so I don't know how they do the instructions. I will say your blocks look great!