The reason that you cannot edit the main sheets of the Google Sheets, is to ensure a robust and continuous sync between your data backups and the Google Sheets.
However, it is possible to make edits and build reports using the two extra sheets: Pivot and Charts. These sheets allow you build dynamic reports on top of your backed up data.
What happens if I do edit a sheet?
When you edit the sheet (e.g. removing a column), then we will archive the sheet and create a new one instead.