Thanks to the remarks by Vivek Kumar and Arunkumar Deshmukh on my Facebook post, it is clear that there were two Dinshaw Billimorias. First one started out as an actor, then became a color film technician in Film City under JFH van der Auwera. [Incidentally his elder brother Eddie was also an actor, later character artist.] The second one started out as an assistant to Chandrakant Pandya as a recordist and then becoming one himself, winning the Filmfare awards for Bandini and Agent Vinod.
Harish raghuwanshi in his book, 'Inhen na Bhulana' writes that the actor Dinshaw worked in the Sound Department of Film Center in the beginning.
So, which one is the assistant in Aurat (1940)? It turns of that the Chief Sound Recordist for that Mehboob film is Chandrakant Pandya. So, it is reasonable to assume that it is the second one, who was never an actor.
The documents have small print, and, may be difficult to read as images on cell phones, so, I combined them into a pdf.
The Filmlfare one is from my collection, the other two are given by Vivek Kumar. Thank you very much Vivek Kumar!
DINSHAW DOCS
Now You Know!