When key images are exported using the export_key_images command, each key image is signed using the private key of the output corresponding to each respective key image.
This signature will prove that the signer knew the private key for the output.
However, does it prove that the key image being signed really is the correct key image for that output?
This has implications for an auditor that wants assurance that the key images provided are not made up in order to conceal the spending of a view-only wallet's outputs.