I just saw today that Iwan feeds DT's (he has clams though) and that tidal gardens website mentions that feeding DT's does not directly feed SPS, but can increase other planktonic species which SPS can feed upon. All anecodotal of course
I don't know, many in the SPS don't use it and have stellar tanks.
I think I'm softening my view on it some, just montior your PO4 levels carefully.