In 1931 Rutherford disbanded the Editorial team that Russell had stipulated in his Will. This was so that they would not interfere with Rutherfords flow of marvellous spiritual gobbits.
So, from 1931 until his death (1942?), Rutherford's pen alone produced the W.T output of doctrine.
So, he must have, alone, been the FDS for those years, no one else was performing the function that the Noo Lite says is done by the FDS during those years.