Knowledge of an industry or, more important, the people in it, their prejudices and preferences must give a candidate an advantage. It makes possible advice about how to present an application which will get you to interview. No one can get you a job. If nothing else, it helps to get you to interview. Here is another possible explanation why both OA and RFEA appear not to place directly more candidates.
People use the advice to sell themselves into jobs of which neither agency has been aware.
Nevertheless, there are many employers who value the work of both bodies. The following is an extract from a letter from a large commercial organisation written several years ago. That letter was written before the present arrangement came into force. Nowadays, reference to one office would make the vacancy available across the entire partnership. The number of firms making use of the two ex-service associations is increasing as they become better known.