If I backed up because he told me to, then no. If I told him I wanted to back up 600 yards, then yes. He did his job.
But if the guide wanted me to back up 600 yards, I'd tell him to lead the way, after I shoot! Of course, this all assumes it is legal - as in I have a tag, it is a legal animal, and I would shoot him at close range or 600 yards.
Realistically I'll never be in that situation. I limit my shots to 400 yards.