Interestingly, neither the web page nor the previous threads address that the colors in the book might have changed/faded over the centuries, depending on the dyes used. The pages probably didn’t get significant light exposure, but heat and chemical factors might have had an impact. And, of course, the photos might not be completely color-accurate.
They definitely aren’t. Pantone books expire after 18 months or so. Color accuracy is near hell at the best of times and even today we’re dependent on humans to validate matching. Printers don’t rely on digital tools for this because they require constant calibration.