While updating or re-installing iOS with iMazing, iTunes launches automatically and offers to Setup as a new device or Restore from a backup.
During the reinstall process, iTunes incorrectly detects the device as a new device. This detection is automatic and it is not possible to prevent iTunes from launching.
You can safely ignore this iTunes message, quit iTunes, and let iMazing finish installing or updating iOS.
Choosing 'Set up as new iPhone' or 'Restore backup' in iTunes while iMazing is still working can cause data loss.