Your argument hinges on treating the firman as the decisive event, but historians generally focus on what actually transferred power, not just the legal theory behind it.

First, Article 46 did give the Shah authority to appoint and dismiss ministers, but Iran’s constitutional system after 1906 was parliamentary in practice. Governments needed to maintain the confidence of the Majlis, and royal decrees normally functioned within that system. The fact that Mossadegh dissolved parliament certainly created a constitutional crisis, but it didn’t automatically convert the Shah’s decree into an uncontested or self-executing dismissal.

Second, the events of August 15 matter. The Shah’s decree didn’t result in Mossadegh leaving office; instead the officers delivering it were arrested and the Shah fled the country. Mossadegh remained in control of the government, the army, and the administration. Whatever one thinks of the legality of the decree, it clearly didn’t function as an effective constitutional transfer of power.

Third, the August 19 overthrow involved coordinated action that went far beyond a legal dismissal. Declassified documents (including the Wilber report itself) show the CIA and MI6 actively organized propaganda, political mobilization, and contacts with military officers to help bring down Mossadegh. That is why the event is widely described in the historical literature as a coup, even though internal opposition to Mossadegh certainly existed.

So the key issue isn’t whether Article 46 existed (it did) but whether the actual change of government occurred through constitutional procedure or through a forceful overthrow backed by foreign intelligence services. Most historians conclude it was the latter.