Why did Justin Vernon not take credit for his vocals in Fall?

Justin Vernon said on twitter while responding to a fan that he was not in the studio for the Eminem track 'fall'. On the track, Eminem takes shots at other rappers like The Creator, Arcade Fire, Earl and Tyler.

I think the reason Justin did not take credit for his vocals on the track is because he is not a fan of the message on the track and he asked that the track should be changed but it wasn't. Justin reveal this in a series of tweets.

In other tweets, Vernon said he thought Eminem is “one of the best rappers of all time. This is not the time to criticize Youth, it’s the time to listen. To act. It is certainly not the time for slurs.”