Txurce
Deity
Its certainly possible that the AI is hard-coded not to attack again for 30 turns, though I think (but I'm not positive) I've seen it do so before then.
But it still misses the point, which is that the human player can currently re-initiate hostilities after only 10 turns.
I just tested this and you are right that hostilities can be re-initiated after 10 turns. This is unfair to any AI that pays through the nose for peace, so the 10.5 change to 20 turns is a very good one, in my opinion.