If you want to know the details you can read all my previous comments and follow the links from here - https://news.ycombinator.com/item?id=37692617
If I had to bet though it was a security thing. They want caste named explicitly because a good deal of Indian immigrants are dealing with it despite it supposedly being illegal.
If you want to know the details you can read all my previous comments and follow the links from here - https://news.ycombinator.com/item?id=37692617