The OCG/TCG version of this card's Pendulum Effect is sort of the opposite of its anime counterpart. While the anime version changes the Level of a monster's Level equal to any other monster's Level on the field, the OCG/TCG version changes the Rank of its controller's Xyz Monster equal to the Level of another monster on their field.
Wu Xing, also known as the Five Stages (Wood, Earth, Water, Fire, and Metal), is a fivefold conceptual scheme that many traditional Chinese fields used to explain a wide array of phenomena. In the creation cycle (相生 xiāngshēng), one elements is generated or created from the other.
This may be reflected in the Pendulum Effect of "Xiangsheng Magician", where it can be interpreted as it "generating" enough of the targeted Xyz Monster's Rank to equal the Level of the targeted non-Ranked monster.