I have an educated guess about the difference between the lyric in books and the lyrics in songs. They often change songs or lyrics while recording them. However, the lyrics have to be copyrighted prior to the booklets being printed. Therefore, whatever lyric version was copyrighted is the one that will be printed in the booklet or distributed in whatever fashion. They don't have time to re-copyright the lyrics before the booklet has to go to the printers. That seems logical to me!

Becky