It's very individual feeling.
I guess you right , it's mostly of individual perception, because ,for untrained ears, most of the noise music sounds equal. But if smb listen to nothing but noise and PE for a few years, sooner or later he starts to recognize the differences between artists , techniques, subgenres etc. However, straight speaking, the most of noise that produced nowadays is actually very similiar, and the modern noise trends are wierd enough .
Most of the noise and harsh noise wall artists have no concept at all, but only explanations as "experiments with sounds".
This is it, and , but a very few exceptions , it always extremely boring. Say, Lasse Marhaug, Kevin Drumm, Daniel Menche are exactly that kind of noise artists. Their art is just a filler for a modern art galleries and a toy for floсks of hipsters.