even if your writing is influenced by "the AI style," it would likely only show up in patches, a word or rhetorical flourish maybe, but AI-generated text doesn't "sound like AI" in patches, it does so consistently across the entirety of the output. it's very hard for a person to maintain the syntactical patterns of AI writing over an extended period of time unless they know exactly what those are -- probably more knowledge than any person currently has, really -- and are applying a level of detail to each clause comparable to forging a painting.

there's also the fact that "the AI style" has changed over time. for instance, the word "delve" is notorious as an "AI sign," which it was up until mid-2024, at which point it dropped off sharply and has now basically disappeared from LLM output. so if someone happened to pick that up due to reading it everywhere, their writing is now less characteristic of AI, not more.

I might be missing something but what’s the real story of the 20%.

To me it sounds like 1. Either your tool is just not that good and reliable as you thought, 2. AI is trained on human written articles, so some of that human written content informed the now established “AI slop”.

There are people who shipped “slop” before AI.