Yes, I follow the song when watching the video, but I shouldnt really have to watch the video to be able to read the music in the book, especially as there are songs in the book with no video. Shouldn't the book be telling the reader exactly how many strums per chord for every chord if you are using it to play a song? I thought it must do this and maybe I was missing something?
Re the intro, are you saying it should be 6 strums on the first E even though the book doesnt show this (it shows 4) or are you saying Justin is adding two extra strums that wouldn't ordinarily be there music wise, but he's improvising or doing it rather than counting the appropriate silent space before the next chord?
Sorry if I'm missing what you are saying, but I'm still not sure I understand if the songbook does tell you the strum numbers for every chord for every song or not, and if it does how do you know the number of strums if there are no bar lines?