Actually that is absolutely true, corals do utilize nitrates. Remember, the beneficial zooxanthellae will utilize nitrates for growth. The reason we keep nitrate low is to prevent the extreme growth of the zooxanthellae, which actually causes the coral to reduce its growth rate substantially. Organisms such as anemones, algae, and coral will utilize nitrate, but the soft corals appear to be the ones which benefit over the more calcerous corals; the theory is that the elevated nitrate causes the host coral to compete with the zooxanthellae for inorganic carbon (the study was conducted using Porites compressa).
This comes from Advanced Aquarist magazine, August 2003. It's a bit out of date, and I've not updated myself as to the literature, but point being is that adding corals can reduce nitrate levels, if the research is correct.