The .summaryElement accessibility trait causes VoiceOver to announce that element when the app starts. The element won't get the focus though, and the order is not affected. A candidate for this trait could be the rings info in the Activity app.

The Activity app is opened. The focus stays in the Summary heading, which is the first element in the app. If the activity rings had the .summaryElement accessibility trait, VoiceOver would announce: “Moving 55%, Exercising: 8%, Standing: 38%. Summary, heading”