MetaRover does not directly collect, use, store or transfer your data. What you do in a Google Sheet with MetaRover stays in the Google Sheet unless you decide to move the data elsewhere yourself.
The only storage means MetaRover uses are the Google Apps Script User and Script Properties stores which are accessible only to the Apps Script that runs associated with each user’s instance of MetaRover. This data allows for the scheduling of Cron job type Triggers through which MetaRover can continue to check meta values for URLs in a sheet containing multiple hundreds or thousands of URLs while you do whatever else your heart desires. You can delete scheduled Triggers via the Manage Triggers menu in the MetaRover Add-on.
MetaRover does use the default Google Analytics collection allowed by Google for Apps Script Add-ons. This should provide the Add-on developer with anonymous usage data that could help with future enhancements to the Add-on.