Dear Laura,
Good day! Thanks for posting in Microsoft Community. We're happy to help.
From your description, it seems that you are encountering issue with user's own sheet view in a shared document via a SharePoint desktop folder via windows 10.
If my understanding is right, generally, this is a by design behavior for co-authoring. Each action in the excel workbook will impact the other user who is opening the file at the same tile.
For your reference: Collaborate on Excel workbooks at the same time with co-authoring - Microsoft Support
We'd recommend you enable the check-in and check-out future in library settings, if you want to make changes to a file on a SharePoint site and you want to make sure no one else can edit it, check out the file. When you finish editing and check the file back into the library, other people can see your changes and edit the file, if they have permission. And, if you decide not to make or keep any changes in the file, you can simply discard your checkout, so you don’t affect version history.
For your reference: Check out, check in, or discard changes to files in a SharePoint library - Microsoft Support
To enable require check out, please navigate to the library > settings > library settings > More library settings > Versioning settings > Set require check out to yes > OK as shown below




Additionally, as you mentioned you are" accessing the document via a SharePoint desktop folder via windows 10". May I know if OneDrive sync client in use? If so, we can also pause OneDrive sync for a while, and uncheck the option to "Use Office applications to sync Office files that I open" to avoid the impact, this will also interrupt the co-authoring.
As our product developers are willing to hear the users' suggestions, I kindly suggest you submit your feedback on the Feedback platformto our product developers so that they can know your requirements and ideas for product improvements.
If the scenario above is not consistent with yours, you can also post back and point that.
Thanks for your understanding and have a nice day!
Sincerely,
Rhoda | Microsoft Community Moderator