It's BIAB so I don't sparge. Like I said, when I don't use dark grains I just add a bit of lactic acid (about 5 ml to 10 gallons of water for a 6 gallon batch).
I realize that dialing in a proper pH with dark grains reduces tannin extraction, and realize that tannins are mostly a product of temp and pH, but I like the Gordon Strong analogy regarding using freshly brewed coffee or coffee that's been heated all day. I notice that when I steep cold tea it tends to taste better than heating tea and then cooling it in the fridge.
The question really becomes, can one combine cold-steeped grains with the properly pH mashed base malts at the end of the boil or later? Or will the steeped grains lower the pH so much (say if added to the fermenter) that it will negatively affect fermentation?