Ahriman
Tyrant
Culture-focused major civ cities build cultural buildings.
Cultural-focused CSs do not.
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∴ Capturing a culture-focused major-civ city gives a personality-dependent bonus, while doing so for a minor civ does not.
Here's your logical flaw.
Culture-focused major-civ buildings construct culture buildings *instead of other buildings*.
A culture-focused civ that has more culture buildings will have fewer research, military and gold buildings.
They don't just get *extra* cultural buildings for free.
They don't get to change the rules that say, a building costs X hammers to construct.
So there is no logical connection between:
Civ A has a flavor value and Civ A has more buildings.
Flavors only change relative priorities, and (I think) military units are one of those priorities.
There's an empirical way to test this. Run an AI game simulation. Observe what buildings each CS has on turn 150, 250. Observe what buildings each AI player has in each city on turn 150, 250.
Compare.
Make sure you do this for a range of AIs, including conquest-oriented and expansionist ones like Mongols, as well as peacenik builders like India.
I do not think you will find that AI cities on average will have more buildings than CSs.