I think the point is that the AI is part of the game and the game had perfect knowledge about the player.
If you're trying to make a bot that plays the game with only the information the player has then that's cool and interesting. But if you are designing an AI as part of the game then you're making them not consider their perfect knowledge by adding restrictions.
If you're playing a poker game then of course the AI knows what's in your hand. Telling it to purposefully play subotimally and telling it to not consider the player's hand to me is equally artifical although one might lead to more enjoyment.
The game knows, but the game is not the AI. It's an adjudicator, making sure that everything happens according to the rules. The AI is a component of the game (viewed as a whole) in the same way the player is.
A poker bot that knows what's in your hand is not playing poker. Not seeing other players hands is inherently part of playing the game. Further, an AI should be capable of using the same interface people do otherwise it's not a game X bot it's a cheating game X bot.
If you're trying to make a bot that plays the game with only the information the player has then that's cool and interesting. But if you are designing an AI as part of the game then you're making them not consider their perfect knowledge by adding restrictions.
If you're playing a poker game then of course the AI knows what's in your hand. Telling it to purposefully play subotimally and telling it to not consider the player's hand to me is equally artifical although one might lead to more enjoyment.