A rookie is a driver new to Realish Racing, no matter what their previous online racing record is like.
The club rules state that a driver new to Realish Racing will be classified as a rookie until:
a) they complete their second season
b) they compete in more than half the races in either of their first two seasons
By this point you would have been racing with the club for potentially up to 6 months - not really rookie territory. Rookie status will still be game specific. A driver can be a multiple Forza champion but still be eligible as an F1 rookie if they are competing in your first F1 season.
A new driver loses their rookie status if in either of their first two seasons they:
a) enter more than half the races in either of their first two seasons
b) wins a championship (rookie or otherwise)
Special events are separate entities and a rookie driver entering, completing or winning a special event will still be considered a rookie as per the rules above.