When creating AXCustomContent objects for accessibilityCustomContent, you can specify the importance of the data. If it is high, it will always be presented by VoiceOver. You could potentially ask the user if that data is of importance to them.
You may also find interesting...
VoiceOver will traverse elements from left-right, and from top-bottom. If for any reason you need to change that order, in SwiftUI you can change the accessibility sort priority. A higher priority number in the container means it will go first.
If you want to know everything about how to "Tailor the VoiceOver experience in your data-rich apps" with the Accessibility Custom Content API, there is a WWDC21 session. https://developer.apple.com/videos/play/wwdc2021/10121/ When implementing accessibilityCustomContent, for any supplementary information, it returns an array that VoiceOver will announce in that given order. The value of the AXCustomContent first, then the label. Users can configure in VoiceOver's verbosity settings if it should say that there's more content available, or play a sound hinting that there is, or simply do nothing. So it should really be optional content as users might miss it.
You can add an observer to listen for changes in the content size category, in case it is more convenient than overriding traitCollectionDidChange(_:).
