I think they under produced it on purpose to make people want gold more
So let's do an economic thought experiment here.
I'm apple, i'm prepping to launch a new smartphone I know will have massive appeal globally. I'm not 100% sure what colors will be the most popular, but I know from surveys i've done in various countries that I can get some idea of what to produce.
a) I could produce everything equally (1/3rd each) and distribute equally (every country gets 1/3rd each).
a.1) I could produce everything in the max capacity possible and end up with higher proportions of some colors because they are easier to produce
b) I could look at the data i've gathered and decide that certain countries will purchase more of X color and give them a higher portion of that in order to sell out fastest.
c) I could underproduce/underdistribute a color I don't think people will want in order to artificially drive up sales of that color due to a perceived scarcity.
d) I could underproduce/underdistribute a color people will like in order to artificially drive up already high demand
It seems to me that since many, many people are discussing how badly they want gold, not that it's scarce but that it's the one they lined up for, and that many observers have said the Gold color was aimed at an Asian market that likes Gold products, that it would make very little sense for Apple to artificially hold back gold units for no other reason than to increase a demand for something that already exists.
More likely is that they gave Asia more Gold units because Asia likes Gold units, and more likely than that is that it was harder to produce Gold for some reason (or they didn't find out about the demand for it until after production had started).
Of all of the possibilities, the chance that they made you wait for gold just to make you want it more is, in my mind, insanely unlikely.