I think you're technically right, but that this will be overlooked from a legal perspective because it's less obvious that humans have been training ourselves on the prior art of others. We tend to blend in additional things besides prior art. (eg. nature, sensations, etc.)
But you've seen many PD images reshared by stock imagery companies. It raises the question of why false assertions of ownership aren't easily prosecuted, given that they constitute a kind of fraud upon the public.