Sourdough Breadmaking: Adding Water to Dutch Oven to create more steam?
What you are doing essentially allows the bread to rise a little more before the crust toughens. It will leave you with a lighter, fluffier loaf with smaller air pockets and a softer crust. I have never poured water into the dutch oven before, but I often just wet the loaf right before putting it in. You can do that with a spray bottle or basting brush.

I'm not sure how exactly your method will differ in results though, as it will do 2 things: rapidly lower the temperature of the dutch oven (transferring the heat to the water) and start cooking the top of the loaf faster.