I agree as this kata https://www.codewars.com/kata/595a4838d41def8ef2000017 is identical to this kata but the solution I wrote for that kata doesn't work for this one.

Why is the second BST in the example a valid BST? (root = 7, leftChild = 9, rightChild = 2). For BST , for a node with key k , every key in the left subtree is less than k and every key in the right subtree is greater than k. Thus the second BST in the example shouldn't be considered a valid binary Tree. More info (https://www.tutorialspoint.com/data_structures_algorithms/binary_search_tree.htm)