No they are not graded as final if their is an error in grading.
Sometimes books will make the honest mistake while others will just make the rules up as they see fit. For example
Sportsbook.com recently stole players funds and cited correlated parlays were against their rules. Also That same book (SB.com) also canceled wagers on a baseball game and claimed it was do to using the wrong initial on their listing.
If it wasn't for watchdog sites like SBR looking out for the players best interest in those "grey area" rules. I'm sure more books would try to pull more stunts like that.