Using threes is common in English writing and speaking. It has an optimal balance of expressiveness (three marking a pattern or breadth; creating momentum) without being overwhelming.
It’s not uncommon, as basic writing advice, to use sets of three for emphasis. That isn’t a signifier of LLM generation, in my opinion.
This excerpt is demonstrating the use of a literary technique to write non-literary prose. It's an almost sure sign that an LLM is generating the text.
It's also seemingly the only way ChatGPT knows how to write, while being very uncommon for blogposts beforehand. Of course it's not 100% proof, but it's the most likely explanation.