Yet... I know this sounds arrogant, but I feel like I would eventually realize they're real photos if I stared at these long enough without being told. i.e. If I saw them framed on a wall and walked past them every day.
The image noise, surface imperfections, chromatic aberrations, etc. are clues, and yes a raytracer can reproduce that, but not usually this well. That's precisely why I think these are beautiful.
I don't think I would notice it out of context though...
It is slower to render than using "thin glass", and lighting the checkerboard surface underneath the glass isn't as efficient (you can't do naive Next Event Estimation through the refraction of the glass volume, but you can do manifold walks to solve that), but we do it at that level of fidelity often enough when required and have been for years. There are times when it's not required though, so approximations can be acceptable in more forgiving situations.
But if we found a thousand different versions of that scene in CGI, I would bet that every single one of them would use a checkered pattern plane that's slightly reflective. Maybe even uses marble subsurface scattering. But none would add a sheet of glass on the plane as a not-forced modelling choice. That's what makes the photo identifiable as a photo.