Definition of In-order Traversal

Question

In the Tree abstraction, that is currently being written(as code practice),

/************ tree.h *********************/

.....

/****************** Usage-start ************/
#if defined(LCRS)

  typedef struct LCRSTree Tree;

#elif defined(MULTI_WALK)

  typedef struct multiWalkTree Tree;

#elif defined(BINARY_TREE)

  typedef struct BinaryTree Tree;

#else

    #error "Invalid representation\n"

#endif

  .....

typedef void(*visitFunc)(void *);

Tree * newTree(void);
bool destroyTree(Tree *);
 ...
void preOrderTraversal(Tree*, visitFunc);
void postOrderTraversal(Tree *, visitFunc);
void breadthFirstTraversal(Tree *, visitFunc);

void inOrderTraversal(struct BinaryTree *, visitFunc);
.....

#endif  /* TREE_H */
/**************** Usage-end ******************/

---

inOrderTraversal() is declared as,

void inOrderTraversal(struct BinaryTree *, visitFunc);

which mean, inOrderTraversal accept binary tree but not N-ary tree(N>2), unlike pre-, post-, breadth first traversals.

Idea is inspired from this answer, where it says: In-order traversal is a special case. It probably only makes sense for binary trees.

Question:

Before final code change, Please confirm my understanding on usage of inOrderTraversal() in the above code.