As many people, including me, suspected the photo of Surendranath that I posted in the previous Musing was wrongly labeled. The surname 'Sen' was a mistake.
I was able to contact his son Kailash Surendranath on Whatsapp and he confirmed that he never used a last name. He also said that his grandfather called himself Pundit Ralia Ram Sharma, so that is their last name. But he re-iterated that nobody in the family has used the Sharma last name.
And he is definitely BA, not MA.
Here is his entry from the Indian Motion Picture Almanac & Who's Who (1953).
Now You Know!