I suddenly developed a headcanon. If Yuu (the player) was suitable for Heartslabyul they would have been part of ♦️ suit. Because ADeuce combo can be counted as "one-eyed royals" (kinda), since their marks are big and literally on their eyes, NPCs with same suits don't have marks as big as Adeuce.
One-eyed royals contains K♦️, J♥️ and J♠️. Yuu is prefect defacto dormhead and supposedly equal to Riddle who is the Queen. So making them King don't seem strange. ADeuce combo and player tied to each other. So making them ♦️ could be justified.
Oh-ho, now that's a good theory!! And it makes sense, all things considered.
MC is, technically, a Dorm Leader in their own right, as the head of Ramshackle, and is also something of the Leader of both the trio they formed with Adeuce, and, in a manner, the first year group as a whole. Giving them the King fits, while Adeuce are the lower royal Jack cards, being regular students.