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While this is strictly speaking 'true', I don't think I understand what else you'd want.
Games themselves offer a limited possibility space to players (or they'd be impossible to think about 'balance' in), and therefore any AI will also have a similarly limited possibility space.
AI is about learning the conditions under which to utilize parts of that possibility space. That's nearly always just a small stored Neural Network map on top of the standard machine state anyway.
The 'AI' part has moreso to do with the fitness algorithm over time, which isn't really that hard to do since MMOs can just apply weighting to the 'experiences' of top level bosses. They don't even have consistent experiences.
The game also could add this later, by just 'logging' the entire battle from the boss' perspective and then feeding it back into the system with as many tweaks as necessary, as many times as the team sees fit. So my question would be, what's the difference, other than 'scope'?