I have a tab book for "Black Sabbath" and the song "Iron Man" for example, it has a key signature of
bbb. I know this song is played in standard E tuning, and eg the main riff starts with a B + F# power chord on fret 2 string 5. However, the book I have seems to have all the fret numbers bumped by 1, as though the guitar were downtuned a half-step.
Is it normal for key signature changes to modify what a tablature shows, or is this tab book wrong?
The book is "Black Sabbath Anthology" ISBN-13: 978-0-8256-1084-4 by Amsco Publications, for reference; attached is a photo of the 1st page.