CareerCup

In the CrackingTheCodeInterview book solution, CareerCupLibrary - TreeNode, the isBST method is like this:

public boolean isBST() {
		if (left != null) {
			if (data < left.data || !left.isBST()) {
				return false;
			}
		}
		
		if (right != null) {
			if (data >= right.data || !right.isBST()) {
				return false;
			}
		}		
		
		return true;
	}

But I think this method only checks whether the tree is searchable, it can NOT check whether the tree is balanced. Am I right folks?