Aah. So I couldn't make a wonder that adds '10% culture while the empire is happy'?
Sure you could. What I was trying to say is that you'd make a building that has no effect. Then, in Lua, you'd make an end-of-turn event that loops over players, loops over each player's cities, checks to see if that city has this wonder, and if so, get that player's Happiness. If it's positive, then get the culture per turn and award an additional 10%. It'd work just fine, at least mechanically.
The problem is that the AI would have no clue that building that wonder leads to that effect. It would build the Wonder, based purely on the Flavor ratings, and would then get the effect without knowing why.
To illustrate, consider the following three effects:
1> +10% culture
2> +10% culture when happiness is positive
3> +10% culture when the player has more than 1000 gold in the bank
The AI literally can't tell these apart; all it can be told, through the Flavors system is "this wonder is good for culture". #1 it can handle just fine, obviously. #2 it technically doesn't handle well, but since the AI already prioritizes keeping happiness above 0, it's not really a problem. But #3 would be a problem, because the AI is not currently built to save up money, and there's no easy way to make it do so.
It's possible that the existing XML stubs (like the ones in the policies you're asking about) are tied into the logic a bit more directly, to where the AI CAN be told to account for these conditionals. But Lua-based logics definitely can't.