Depending on the quantity and type of steeped grains, the pH reduction may be notable or not. In an Irish dry stout, the pH reduction is an important flavor component. In other beers, it may not be appealing to drop the kettle pH by a few tenths. Whether the grain is added in the main mash, at the end of mash, or the kettle, the pH will be reduced. You will have to decide if that drop makes the beer more appealing or not.