But that's not recursion, which pretty much by definition implies the use of repeated invocations of the same function(s). Explicitly building a stack is exactly what the article was discussing, though it's far more clever than the obvious approach. I've seen AVL implementations that use an explicit array for maintaining a stack in lieu of recursion or parent pointers.

In any event, you always need a stack of some sort. Recursion is one way to accomplish that, but saying that you're simulating recursion by explicitly building a stack reverses the categories.