Hey drfaust,
I don't know the answer, but my guess is you applied for SO as you don't have the time for FO even though you have the rating. I guess you'll be dealt with as a rated SO same way a rated FO would be. OCC as you said followed by their extensive line training for an SO.
Would you care to share the timeframes with me?
How long after interview were you informed of success?
How long did it take to get your formal offer?
How long after interview to start date?
Many thanks
PW