Regarding the four sons of the Seder that are mentioned in the Torah, only 3 of the sons ask questions that seemingly relate to the laws of Pesach: the Rasha, Tam and She’eino Yodea Lishol. The Chochom's question isn't specifically about Hilchos Pesach. Rather, his question is a general one about why there is a difference between the different types of Mitzvos; עדות, חוקים, and משפטים, if they are all commands of Hashem. So why do we include his question?
The answer is simple. We don't want to leave the Chochom out of the Haggadah, especially as we are dealing with the rest of the sons. Since we don't want to leave him out and since he asks about the Mitzvos that are Eidus which includes Pesach, we find the way to bring him in.
~ Second night Seder 5704
