Reply to "Cornstarch in Sugar Cookies?"

Yes, the substitution of cornstarch for a portion of the flour is a typical way to "soften" or "lighten" the crumb/texture of all baked goods, ranging from cookies to cake. The gluten in wheat flour leads to a more textured, resilient, and sturdy dough in general, so when you remove some of it, the texture of the end-product gets more delicate. I suspect the lack of spreading has more to do with the fact that the baking powder was removed, however.