I think you are misusing the term "perfect information." In this case, chess is a real world game where both players have perfect information. That is, neither player can keep a secret of where any of the pieces have moved.

So, the complexities of how the AI is taught to interact ultimately don't matter. It may have a lot of effort to parse the visual of the board to get the perfect information, but the game is defined as one of perfect information.

Wikipedia calls out that there does not seem to be consensus on what this term means for games with chance or concurrent play. https://en.wikipedia.org/wiki/Perfect_information