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.
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.
There is also documentation available that describes the behaviour of this tab and button https://docs.unity3d.com/6000.5/Documentation/Manual/upm-ui-details.html.