We have a workspace, which is the new kind of workspace. We published one report to the workspace from Power BI Desktop and created an App from it. The workspace was then moved into a premium capacity. We then published a new version of the report from Power BI Desktop. When we tried to update the App a new app with exactly the same name appeared. The old one was still showing the old version of the report but the new App showed the updated report. We then did a unpublish App from the workspace and the old App disappeared while the new App is still there. The workspace still shows Update App instead of Create App even though we unpublished it.
It all seems to work now but we thought it was impossible to have two Apps with the same name and this certainly sounds and feels like a bug.