Notice rules are ordered. You don't optimize until you know you need it. They started with a data structure they though would be fine. Clearly it was fine since it worked and they decided it was later worth optimizing.

The existence of 1.1.1.1 speaks to a much larger design problem. If you want to talk about what should have been done, you need to step much, much further back.

It can be. Sometimes you take a profile and there's a big smoking gun and nothing else matters.

Sometimes it's a lot of small things everywhere and you can pick up significant performance after a lot of small value fixes. In this case, caching wire data instead of structured data is almost one of these, because the contribution to response time for serving a cache hit is small... otoh it happens so often than a small improvement matters; but this is a pretty focused use case, you usually hit the many smalln improvement issue in a less focused application where there are many code paths.

Sometimes the whole code structure / data structures are so wrong, but it works and perf is bad and profiling will never tell you. This article is not that case; these data structures only needed refinement.