Hi,
Thank you for querying in the forum.
From your description, it seems you want to remove an old SharePoint sync folder from File Explorer.
Generally we can use the method in the thread you shared to remove OneDrive sync folder from File Explorer.
To better understand the situation and help you do troubleshooting, could you please provide information below?
Note: to share screenshots with us, you can use the Insert image button to upload screenshots in reply:
1.In File Explorer, please capture a screenshot about all OneDrive and SharePoint sync folders. And please point out the folder you want to remove.
2.In Registry Editor, please provide screenshots about "I don't see the folder with the name I would expect it to be. I see two rows for two items similar to the screenshot shown by the Microsoft Agent,".
Appreciate your time and effort.
Best Regards,
Tina