I think that is extremely common in adverts (most famously here, the M&S "It's not just bread. It's our stone-baked, hand-shaped artisanally-molested bread"), and narrative media like that distinctive kind of journalism written like a storybook, and which (I think) then bled into popular media like true-crime podcasts: "It wasn't just Tuesday. It was the last Tuesday he would ever see. <intro music>".

Also this kind of short sentence construction is used in the incredibly annoying and pervasive style of headlines for opinion pieces: X is Y. And it's Z. (where Z is often "not OK" or "OK").

I assume all this overuse is where LLMs picked it up and weighted it highly.

Is this itself an AI generated comment? The word "just" appears 1 time in the article.

The term “not just” doesn’t appear in the text.