Hi Matt ,
Good day.
Hope you are doing well you for posting in Microsoft Community.
It seems that you want to move an Excel file that contains a Form, from one SharePoint online Documents library to another library.
Based on my test result and finding, I can move the 'Forms for Excel' via Move or copy files in SharePoint function but when I submit an answer from the Form, I'm afraid it doesn´t updated the Excel anymore, most probably because the path changes.
After moving to another SharePoint library, if I can consider using a new workbook to record the responses from form, you can go to the form in Microsoft Forms app > Reponses > More options “Three dots” > Sync all responses to a new workbook.
In this scenario, a new workbook will be created in the default document library of the SharePoint site instead of another SharePoint online document library.
Please provide your feedback on the Microsoft Forms Community in order to help address this concern .
I hope this helps let me know if this is contrary to what you need, I would still be helpful to answer more of your questions .
Best Regards
Microsoft Community