Contributing my own perspective to this interesting discussion:
There are degrees of photography puritanism and every purist is convinced he has the right doctrine. I've interacted with a purist here on POTN who thinks that even recovering modest shadow detail in Lightroom is no longer photography and other people doing it and passing it off as photography rubs him wrong. Personally I'm pretty liberal about the subject of crafting art from photography: if it looks good as art then it is good as art imo. However, that's a great big IF. If you're going to fake something - sky replacement, background replacement, compositing, adding lighting effects, etc. - then it damn well better look great - it better look believable or it falls short of being good art.
I think architectural fine-art photographer Joel Tjintjelaar does amazing work, but it's way more crafted/contrived/fabricated and is less representational of actual reality than Serge's images with the added light rays. The difference is in the results. Joel's work looks insanely good, while Serge's photos with light rays look goofy and silly by comparison. BTW, J.J. Abrams destroyed his first Star Trek movie by adding in 721 lens flares throughout the movie imo; painful to watch!
Summing up, for me the issue isn't fakery, because I suspect nearly every photographer does something fake, but rather it's just about the quality of final results.