Don't know about that, but I too was not a fan of his until I saw him live (Lincoln, 1971). He really was GOOD as a performer. (Still is, I suppose?).

Some songers come over much better live than on recordings, and there are also those who sound good on recordings, but are a little disappointing live. Sandy Denny and Ralph McTell were also at the same festival, and neither was as memorable.

Another performer at the same event who made a good impression was Buffy St Marie.