As with a similar question of the expectation gap, all of the above do help as they try to manage the expectations of both parties and close any information gaps.
Postulates are the assumptions that auditor makes in carrying out their duty; for example that the financial statements are verifiable, and also that there are no conflicts of interest between the auditor and the firm.
By sharing the audit concepts and making the process and expectations clear in the engagement letter it will help to close the gap between management and the auditor.
However it may not close the gap completely, especially with the public. It is quite possible that certain concepts or postulates are misunderstood my management (or just not read in detail - especially true if they are very detailed). Furthermore this information may not spread clearly beyond specific members of management who are close to the audit, or to the public who may continue to have unrealistic expectations.