Because the track is old, and it was 100% finished and the same as the Billboard clip when Kleinenberg was teasing it in sets and stuff.
Besides, Billboard said "shape shifting dance legend", which CAN describe Kleinenberg, he is shape shifting (using dogs as his identity and IDK all that) and a dance legend for people who follow the DJ scene etc.
This must be a release they want to hype big time because they see its potential for success, and I think it's his first release with Spinnin Records, so it makes sense to hype it up a lot.
I know he favourited a tweet that said it was the new Madonna single, but he favourited a bunch of tweets that had the link to the song. I think he just enjoys the hype. He isn't denying it because he's not supposed to say it's his track yet.
The Madonna camp SHOULD deny it though, that's annoying me. If she's still in the studio, its highly unlikely she's about to release a track.