Answer for find min/max height of BST incorrect?

https://forum.freecodecamp.org/t/freecodecamp-challenge-guide-find-the-minimum-and-maximum-height-of-a-binary-search-tree/301641

If I create a tree with min height of 2, the solution (plus an add method) returns a min height of 1. Im using the displayTree function provided in the code, where you can see the tree in the console. Maybe Im missing something here but I believe the tree is correctly displayed, I just think the min height function in incorrect.

Solution code + add function as well as tree construction and display

var displayTree = tree => console.log(JSON.stringify(tree, null, 2));

function Node(value) {
  this.value = value;
  this.left  = null;
  this.right = null;
}

function BinarySearchTree() {
  this.root = null;
  // Only change code below this line
      this.add = function(value) {
    const newNode = new Node(value);
    if (!this.root) {
      this.root = newNode;
      return undefined;
    }
    let currentNode = this.root;
    while (currentNode) {
      if (currentNode.value === newNode.value) {
        return null;
      }
      const direction = currentNode.value > newNode.value ? "left" : "right";
      if (!currentNode[direction]) {
        currentNode[direction] = newNode;
        return undefined;
      }
      currentNode = currentNode[direction];
    }
  }
  this.findMinHeight = function() {
    if (!this.root) return -1;

    function findNodeMinHeight(node) {
      if (!node) return 0;
      return 1 + Math.min(
          findNodeMinHeight(node.left),
          findNodeMinHeight(node.right)
        );
    }

    return findNodeMinHeight(this.root) - 1;
  }

  this.findMaxHeight = function() {
    if (!this.root) return -1;

    function findNodeMaxHeight(node) {
      if (!node) return 0;
      return 1 + Math.max(
          findNodeMaxHeight(node.left),
          findNodeMaxHeight(node.right)
        );
    }

    return findNodeMaxHeight(this.root) - 1;
  }

  this.isBalanced = function() {
    return this.findMinHeight() == this.findMaxHeight();
  }
  // Only change code above this line
}
const p = new BinarySearchTree()
p.add(17)
p.add(4)
p.add(1)
p.add(19)
p.add(33)
p.add(34)
console.log(displayTree(p))
console.log(p.findMinHeight(), "min")

console output:

{
  "root": {
    "value": 17,
    "left": {
      "value": 4,
      "left": {
        "value": 1,
        "left": null,
        "right": null
      },
      "right": null
    },
    "right": {
      "value": 19,
      "left": null,
      "right": {
        "value": 33,
        "left": null,
        "right": {
          "value": 34,
          "left": null,
          "right": null
        }
      }
    }
  }
}
undefined
1 min

Answer not incorrect! The definition of min height is distance from the root node to the first leaf node that does not contain two children!