This is precisely my point though, "stock photography" isn't an individual work. Copyright law doesn't apply because you can't infringe on the copyright of "stock photography" as a whole any more than you can infringe on the copyright of "rap" or "rock and roll" or "oil paintings".
Further, just because a new tech can substitute for a class of old tech doesn't (often, barring protectionist laws) mean the old tech gets to impose legal restrictions on new tech. To trot out an obligatory car analogy, the rise of the automobile was not legally hampered by the fact that it substituted for the products of buggy and whip makers. More relevantly, the rise of photography and cameras was not legally hampered by the fact that it substituted for many painters products. The rise of stock photography itself wasn't legally hampered by the fact it substituted for the work of corporate artists. The rise of point and shoot cameras wasn't legally hampered because it substituted for the work of professional photographers.
Lastly if the argument is about that the tech makes it "possible to fully or substantially recreate any given existing work" using deliberate and specific inputs, well we've had plenty of legal precedent on that too. The same arguments were made about Xerox machines, about cassette tapes, about VCRs, about CD-Rs. The copyright holders pretty much lost in every case. At the point you are taking specific and deliberate actions to knowingly infringe on copyright is the point where the technology used is no longer relevant. The right inputs can be used to infringe on the copyright of Star Wars at any typewriter or computer keyboard in the world. The right inputs can be used to infringe on the copyrights of The Beatles at virtually any instrument. It is the act of infringing, not the technology, which is relevant here.
I believe in some companies, the copyright holders won a concession in the form of a tax levied against each CD-R and cassette tape sold to be distributed to the recording industy. One wonders how the authors of those countries felt about not getting a cut of every Xerox machine sold.
