There is some truth to the handwritten letter.
Last year I was fighting with HDFC to get the spelling of my name corrected on my Neu Card. This is even after having a account with thrm. I sent them all docs via email, they did not consider. Said write a letter to Chennai office. Finally wrote a letter on paper and signed it, then scanned it and sent that as an email and they finally correct the spelling and issues a new card with the correct spelling.
Maybe they want to see how dedicated you are in getting the job done. Email toh koi bhi bhej sakta..