Though there has been discussion on volumes of steeping water, I haven't seen anything on the practice of adding malt extract to your steeping water, thus steeping your grains in wort. I believe that the reasoning behind this is the same as steeping in low volumes of water: to make sure the steeping liquid has a low enough pH to limit tannin extraction. I've also read that steeping in wort may limit extraction of sugars as well. I haven't had any problems with tannic beer, but I was wondering if anyone had any experience or theoretical knowledge in this area.