Its just amazing that you can take such a shot at that ISO. We are so lucky to have cameras that can do this.
Depends on the type of shot - converting to b&w usually reduces a lot of noise and eliminates the problem of missing color accuracy @high iso. This shot also is a good example of texture that is very sympathetic to high noise reduction plus (edge) sharpening - so at this export size, it probably could have been done at iso 102400 and still look the same :-)
Even from your point of view your talking about ISO102400. Lets just assume you are correct and that it depend on the type of shot. Its not so long ago, well within my photographic experience, that ISO 800 was considered high. Now someone can come along and try to prove how clever they are by splitting hairs and saying say something like "well you could push ISO800 film" but whatever spin anyone puts on it from my point of view ISO102400 is just as amazing as ISO12800.
We are lucky to have such equipment.