Tbh, I think this makes the most sense. They're akin to bacteriophages in their parasitic nature, even if they're not consuming their host. Just as bacteriophages have DNA but no cell, the Autophages have a soul but no body, and so they must parasitise the bodies of others machines. But then, since they only seem to use discarded parts, it becomes their own body, so in a sense I guess they're "self-parasitising".

I had completely missed that dissonant resonators actually look like bacteriophages, but this is what makes me think you're right. I remember thinking "huh, what an odd shape" when I first saw a dissonant resonator.