Vinay, I agree with what you have said. While it's difficult for a singer to cross over from tollywood (or kollywood,etc) to Bollywood it's still not half as bad as getting a break. And in my opinion someone with playback experience does have a slight edge. Though in Revanths case he had more disadvantages - language, accent, poor viewership in the south.
But honestly I'm glad that Revanth was allowed to participate. Otherwise we may not have heard such a talent. And you already know that I am a big fan of Revanths. I'm obviously happy he participated and won