When he first singed Rain in PDP, didn't it have half the lyrics it has now? Besides, the melodu changed a lot. So I guess we just gotta wait. It's not that it's an officially release song like Elle me dit, this one can still change.
And for the melody, I'm actually adoring it. Reminds me of Happy Ending, it has the same passion. And yeah, I'd love to listen it only from him too from the bottom of his heart