It's adding an additional class to the protected classes list. It probably didn't fall under any of the previous classes like race, religious beliefs, or national origins. So technically you could discriminate against them based on caste just like you can discriminate against people under the age of 40.
So I wouldn't call it pointless especially given that people from regions who face caste discrimination were the ones pushing for the law. It's not just some cheap PR stunt from a government. It might only affect a very small minority but that's exactly what these kinds of laws are supposed to do, protect a vulnerable group.