Listen to "Concert for Bangladesh" side 3, I think it is. The version of "Just like a woman" sounds great. While it is still Dylans voice, you can see he had potential for singing better. That whole side really sounds good..
EVERYbody has the potential to sing. Some folks just have developed their potential more than others. You do run across the occasional completely tone deaf person, but they are extremely rare and most of the folks who claim they're tone deaf aren't. Usually they just have a natural range that isn't near a standard melody key - so they get frustrated trying to sing the National Anthem at ball games or hymns in church. (They aren't alone in getting frustrated at singing the NA! Most ball game organists start the darned thing too high.) Get 'em in the alto or bass section and they do fine.
But Dylan sounds like a tenor to me.