In my view, be considered “professional photos” is not the best to get a good realism. Do not forget that the company StockFresh take pictures and edit, something very common in publicity photos, for example in this picture you can see an increase of exposure and brightness added digitally. Be very discrete about has to be dark or light in a changed image to be real and convincing.
As this image of the same company, you do not know if a photo or created with Realflow with a rendering engine, no doubt the image was retouched (can be digital retouching or just ambient lighting usually false) so it is difficult or impossible to know whether real or CG.
Anyway, the “error” is in any render engine, let it be unbiased or biased. I took the time to ask without having an “eye-CG” also said it is not real, very fake piano.
What I say is just to comment on an advanced level to which you have, maybe I’m wrong but I’m just saying what I said to my eye.
greetings and congratulations on being in the gallery, however my only criticism is to go beyond.