No, they remain incidental.  The user didn't add them locally, they made a change (intentional or otherwise) to a non-local contact to produce the incidental contact.  I don't think this should ever become a contact that is exported to other sync services.

There is a scenario where this is wrong, but it's massively unlikely:
- sync 'google' contact, without two0way sync
- change avatar on contact, generating incidental
- remove google account, or otherwise stop synching
- see mostly-empty contact (just avatar and name), and decide to populate the other details