The Delft designs are not the Blue Willow pattern. Blue Willow has chinese referenced designs, pagodas and chinese boats, and Delft have Dutch influenced designs, hence the windmills.
There is definitely a difference when you look closely at the pattern. Emblibrary has about 20 Blue Willow designs that can be purchased separately and then combined on a block, or she has a couple of patterns that look like they are straight off of a dinner plate.