The need to treat sparging water has more to do with its initial alkalinity than its mode of sparging. I don't acidify my sparging water because it is RO water with very low alkalinity. However back in Tallahassee, it was pretty important that I acidified my sparging water due to the somewhat high alkalinity of the tap water.
Be careful with assuming that titrating sparging water down to a certain pH will be sufficient for reducing tannin extraction. In Matt's case, I recall that he uses RO and that 5.8 pH target is safe. For someone with really high alkalinity tap water, that 5.8 pH may still leave a LOT of alkalinity in the sparging water and there could be tannin extraction. That is why a pH target is not ideal. A better target is to reduce the sparging water alkalinity to somewhere around 25 ppm (as CaCO3) or less. Depending upon the starting water alkalinity, the ending pH might be much lower than 5.8. However, since we don't need to take the sparging water pH any lower than the mash pH target, a lower pH target of around 5.2 might be the lowest any brewer would need to take their sparging water...regardless of the resulting alkalinity.