Mr. Ramachandran is right in his opinion. Direct recruits are recruited from open market or by call of application from other organisations on deputation basis, not from within the concerned zone of the department. However, if eligible, the employee can also come through the competitive examination conducted by SSC against direct recruit quota. Since SOGE exam is conducted by the concerned wing of the CAG, it is necessarily a departmental exam, may also be a qualifying exam, but only within the parent office where the lien of the employee is maintained.
One complexity in your case may be that the seniority and vacancies of your cadre are perhaps maintained and controlled only on regional basis, like jusrisdiction of the concerned regional audit office. Since you were on the rolls of the AG (A&E) Meghalaya, your lien was maintained only in that office. So, your position in your parent office, of course, was a departmental promotee, but not within any organization outside the jurisdiction of your parent office, i.e., Kolkata. For the purpose of your position in the office of Principal Director of Audit (Central), Kolkata, you were recruited directly on deputation cum absorption basis by calling of applications from various audit offices.
Since you are in the audit department, you are also supposed to know the rules of pay fixation, as various CAG instructions are issued on various matters relating to Government Rules by the office of the CAG for audit point of view. You can, of course, claim any benefit of pay fixation under 6th CPC in the cadre of AAO only in your parent office as may be due for departmental promotees, provided you are eligible under Next Below Rule, if some of your senior would already have been promoted as AAO in Meghalaya office during your deputation period, while you used to hold a lien against your original post. But, if some promotions affected after your absorption in the new post of AAO at Kolkata, you cannot claim that benefit also from your parent office. So, you will have to be contented with your pay fixed with reference to your deputation pay only.
Hope the points are clear to you.