It was not the writing. It was the internal links and the fact that the page answered the question in the first sentence.
A model-drafted page beat a carefully written one because the draft was structured as an answer: entity in the title, fact in sentence one, supporting detail below, links to the related service and location pages.
The human-written page opened with atmosphere. Search and answer engines do not need atmosphere. They need a statement that can be checked against other sources.
We did not replace writers with models. We changed the brief: people decide what is true; models raise throughput on internal links, FAQ coverage and variant titles. The ranking change followed the architecture, not the voice.