It seems to me it worked exactly how I would have expected it. If you choose one GP and start a golden age it automatically picks the needed GP to go with it. You selected TWO GP and asked them each to start golden ages. You got exactly what you asked for. -- 2 golden ages.
So it's not a bug, but I agree it would be better if they designed it to ask you which GP you want to use.
I agree that its not a bug (in the sense that it works as it was poorly designed to work), but you do agree that it is a poor design or design flaw (often much worse than bug), right?
If one accidentally selected one or more Great People than needed for One Golden Age, the Civilization IV code should
not check whether there are sufficient Great Persons to generate a Second Golden Age. It is a UI design flaw to allow Two Golden Ages to be generated when there are sufficient Great People to do so via a single click, unless the Icon clicked clearly means
TWO GOLDEN AGES. The Icon clicked as I understand means a (single) Golden Age, or at least it should in a properly designed UI.
Generating Two Golden Ages accidentally can be a very frustrating and Game ruining experience. The Civilization IV User Interface and code should be designed to minimize such UI accidents. In regard to generating Golden Ages, it has failed the Users catastrophically, both by presumptuously choosing the Great People for the Golden Age and worse for generating TWO GOLDEN AGES when the User (presumably) intended only ONE.
There is also a UI rule violated by the Civilization IV UI code when it selects TWO Golden Ages rather than ONE Golden Age when the Golden Age Icon is selected. If the code selects 2 GAs and the user intended only 1 GA, there's no going back to 1 GA. If the the code properly chose just 1 GA regardless of the number of Great People Selected, the User can simply repeat the process in case he really did want TWO GAs.
Also, always selecting a Single Golden Age is preferred, because starting a Golden Age in a game happens much least frequently than almost any other User initiated action in the Game; thus it is quite tolerable to force the user to click the Golden Age Icon twice to get Two Golden Ages. This relates to a frequency of use related UI rule, where it is acceptable to force a User to repeat an action to get a sequence of two actions rather offer a way to get a single or a double play of the same action (i.e. present a "Single Golden Age" Icon and a significantly different "Two Golden Ages Icon") as that would unnecessarily clutter the UI, despite being presented only when enough Great People to generate Two Golden Ages exist.
I certainly hope that the Civilization V UI designers designed a better UI for Golden Age generation from Great People than what presently exists in All variants (Vanilla, Warlords, BtS) of Civilization IV. After all, these guys get paid big bucks for what they do for us Players, so they'd better get everything done right!
Sun Tzu Wu