The coding quadtree is the whole tree structure that splits the CTU into CUs. Hence saying that a quadtree is split into coding quadtrees is ambiguous as well and would not improve the current wording. Splitting a CU into four CUs would turn that CU into a coding quadtree node while not splitting would let the CU become a leaf and remain a CU. Although the wording might not be ideal, we cannot think of a better wording so we suggest to keep the current one and close the ticket without an action.