The hollowness of oath of secrecy

As I watched the oath-taking ceremony of the Union Council of Ministers live on TV, I couldn't miss the irony of administering the oath of secrecy to the new Ministers as required under the Third Schedule to the Constitution. A careful reading of this oath suggests that it is not against transparency, as it exempts communication or revelation of any matter brought under a Minister's consideration or any matter which was known to the Minister, if the same may be required for the due discharge of duties as the Minister. Therefore, there cannot be a conflict between this oath and a Minister's duty to reveal information under the RTI Act. An RTI applicant can always argue that the information is wanted for the due discharge of duties as the Minister, if the oath is invoked to deny information. I wonder whether any Ministry has invoked the oath to deny information so far under the RTI Act. Why did our Constitution-makers include this oath? Did they really believe that there could be information which might not be required for the due discharge of duties as the Minister, and it was necessary to keep such information under wraps? This 2004 article in The Hindu makes a strong case for replacing the oath of secrecy by an oath of transparency, in line with the recommendation of the National Commission to Review the Working of the Constitution. I couldn't find any reference to the oath of secrecy in the Constituent Assembly Debates; therefore, I am curious how this meaningless oath came to be included in the Third Schedule.