What changed
A Google spokesperson confirmed the behaviour to Search Engine Roundtable →: "For some queries, AI Overviews may dynamically expand for topics where our systems determine it's most useful for people." Google's Robby Stein added a detail that matters for anyone tracking scroll behaviour: "If you've already started scrolling, the expansion stops to keep your place" — so the auto-expand only fires before a searcher has engaged with the page.
Practically, this makes AI Overviews behave more like AI Mode's fully-open answer format on the queries Google selects for it, and it pushes traditional organic results further down the results page than a collapsed AI Overview would.
What this means for SEO teams
This is not confirmed to be rolling out everywhere — Google is explicit that it only applies "for some queries" where its systems judge it useful. But it's one more data point in a consistent direction: less scrolling stands between a searcher and a fully-formed AI answer, and organic listings keep losing vertical real estate on informational queries. If your traffic leans heavily on top-of-funnel, answer-first content, this is exactly the kind of shift our AI Overviews ranking guide is written to track.