Thank you for reporting a bug to Unity.
After reviewing the behavior, we've confirmed it aligns with the current design and intended use of the feature. We understand this may differ from your expectations or workflow.
The "Attached Style Sheets" option is there to display style sheets that are added directly on a VisualElement. Style sheets that are added on the document are not added to all VisualElement inside the document.
We will close this case as 'As Designed.' If you have feedback on how the feature could better meet your needs, please let us know - we value your input and consider it in future improvements.