All this is true. They are a light day workout. They can be replaced with light deadlifts or power snatches.
Fair warning: I realize I am taking interest in a subject of minor importance to the overall program.
In my most recent reading of starting strength the inclusion of back raises for novices caught my eye. By the book's own exercise selection criteria, this seems odd. Back raises are bodyweight, cannot easily be loaded, and don't mimic a range of normal human movement.
Their inclusion seems to my eye to be to break up the frequency of the deadlift. If that's the only goal, why not just rest?
All this is true. They are a light day workout. They can be replaced with light deadlifts or power snatches.
Who needs back raises when we're all doing Squat Mornings amirite?!?