Earlier quoted context omitted.
"Pictures are clearly personally identifiable data, so storing them violates the GDPR if you don't have permission to do so." Wouldn't a Creative Commons license express this permission?
IANAL, but I believe no; the CC license handles the rights that a photographer can hand out, but doesn't come with any kind of model release guarantees.
When you hire a model, photograph the person and then use these photos for promotion or commercial activities, you do require a model release. But in that case it would be absurdly weird to publish such commercial material as CC NC on Flickr, makes no sense.