The on-page search (cmd-F) doesn’t look into closed details elements. Example: search for “rights” on https://codepen.io/gunnarbittersmann/pen/YzezxaK In Chromia it does, and details elements that contain the search term will be opened automatically. (This issue might be related to implementing `hidden="until-found"` as suggested in https://developer.chrome.com/blog/hidden-until-found/)
<rdar://problem/92920374>
I think this is a duplicate of bug 228843.