GM status is usually an anterograde label applied to a previous release that was originally dubbed a beta or RC. So it would likely be more appropriate to state that "beta 5 was certified GM".
Reason being, any time they change the code, they will need to at least do a brief wide-scope beta test to ensure no new bugs were introduced in the previous code revision. Inherently, if the working code is modified, another beta will follow. It's only after that public test trial that they can say the release that is already running and working on many devices is acceptable and stable; fit for general public distribution and then freeze the code and declare it GM.
So in simpler terms, it would probably be safe to say that the final beta release of any firmware version will invariably become the GM and the two will be identical, save insignificant changes such as a change of internal labeling or a very tiny increment in the build number.
But I wouldn't put "stalling" past Apple by any means. Those who have suggested that notion aren't merely paranoid conspiracy freaks!