Bruce, Buffy and Willy can all sing very well.

Leonard doesn't try too. Neil is trying to portray a certain attitude when he sings lead but sings very well in harmony.

Bob Dyan writes lyrics very suitable to reciting in time with music. and he has an idiosyncratic vocal signature where his voice rises in pitch at the end of a line. He vocalizes through his nose in an irritating whiny voice. I cannot think of a single person who has covered a Dylan song, and I have heard many hundreds, who did not sing it better than Bob.

I have never heard anyone say. Hey! That's a good song. I wish Bob Dylan would cover it!

Other than that I will not question the professionalism of a musician who says Bob Dylan can sing.