My assumption would be that, yes, it would increase the GI level albiet not by much.
My theory is that by blending the oats, you are increasing the surface area of the food. By doing this you are allowing more enzymes to come in contact with the oat and break it down faster, thus increasing the rate of absorption.
You can think of it as being the same as Cubed vs. Crushed ice in a glass of water. When you add ice cubes to a glass, it may take a bit of time for the water to cool down because the ice melts slowly. This is due to the cubes having a lower surface area. If you add crushed ice, the glass and water will cool down quickly because there is more of the surface area of the ice in contact with the water. However, you will notice that crushed ices melts in water much quicker than cubes. It's basically the same principle, the more surface area something has, the quicker it can be broken down because more of it is in contact with it's environment.
Hope that makes some sense.