An interesting article. Perhaps not for the negatives in question but the idea that a negative cannot be manipulated is naive. Monochrome negatives, particularly large formats, could be extensively retouched - a highly skilled process as opposed to the software enhancements possible today. Sixty years ago, I had a retouching outfit by Johnson’s of Hendon (remember them?) consisting of a set of very fine brushes and set of graduated grey/black dyes. They were fiendishly difficult to use and I was never any good at it, but newspapers and magazines employed staff full-time as negative (and print) retouchers and the best were very good indeed!
Best wishes
A