It's quite a difficult dividing line to distinguish what personal detail should be in a biography and what should not. I think that the personal stuff which Klein included was necessary to illuminate the private man. I felt that above all, the Klein biography set out to show Guthrie's virtues and faults - and keep some sort of balance. Klein also was in no doubt that Woody was the object of a lot of myth making (not least of all his own), but that the myth was based on a lot of real events and experiences. Klein is very far removed from the gossip columnist who is simply after sales figures. To me it sounds as if Hajdu is one of the Britneys of the publishing world.
More information is always likely to emerge about anybody. No biography is ever really complete. It would probably be unreadable if it was. I think Klein's biography was painstaking, honest, critical and respectful. Maybe enough new information will emerge to make a new biography necessary. I haven't seen the evidence yet.