The reference image isn't linked to any particular iPhone or person:

    We built Apple Reference Image to avoid using an explicit, public
    credential for photographers, and to avoid even implicit public
    association between different photos taken by the same sensor. The
    final reference image is instead signed by Apple’s signing service,
    after validation by PCC. That signature is backed by Apple’s
    strongest technical guarantees.

    Our implementation also protects the
    confidentiality of the image itself, including from Apple. Merely
    capturing a reference image should never expose the actual pixels to
    Apple or anyone else. We achieve this through the exceptional privacy
    properties of PCC — the nodes themselves are architected so that not
    even Apple can access image data, just as Apple cannot see the
    information processed for Apple Intelligence in PCC.