The only wait requirement between each promotion is a simple 3 day wait from Recruit to Builder. Other then that, it isn't a strict system like some people are making it out to be. Everyone gets an equal shot at becoming OP, recruits included. In the end it is admin's decision as to whether we think they are capable- and it happens to be that recruits usually don't get it because we don't know them very well.
In Informer's case, he clearly has loads of experience, not to mention age and maturity. It was not a hard decision to put him on trial.