I think the trees were a lot more useful in the past when memory and caches were smaller (and I suspect they can still be useful for precomputation, though I'd have to sit down and benchmark fixed-grid-with-smart-sizing vs. tree). Trees are also amendable to recursive algorithms but the author has noted that they have reasons to choose iterative over recursive algorithms, so these pieces of advice synergize.

(It is perhaps worth noting: broadly speaking, "recursive" vs. "non-recursive" is a bit of an artificial distinction. The real question is "does a pre-baked algorithm with rigid rules handle flow control, or do you?" If you care about performance a lot, you want the answer to be you, so having your run state abstracted away into an execution-environment-provided stack that you can't easily mutate weirdly at runtime begins to get in your way).