According to Alan Boyd in the September 1998 edition of ESQ, the other Carl interviews were taken from the Time-Life History of Rock 'n'Roll in 1993.
So that means there is probably some good footage there that we haven't seen yet. I liked EH the first time I saw it, but upon repeated viewings, I felt there was too much talk and not enough action...I mean, music (sorry, Paul Revere/Raiders fans). That's why a longer presentation would be better. Feature complete performances as much as possible. Also, I found Mike Love at his most annoying in EH. "Ultimately, I think the Beach Boys music meant so much to so many people because of the positivity - that was MY contribution! Brian was melancholy!" Gawd, someone shut him up!