I wasn't saying it was. Simply that, since the warp is a fundamental metaphysical layer of reality in that galaxy, perhaps it is inherently part of pretty much all life because live evolved alongside it, forming what the Culture would classify as symbiotic relationships with the warp lifeforms known as souls. Basically, 40k people could need their souls in a way that Culture citizens don't, despite both having souls, because 40k folks evolved alongside souls, while Culture citizens just got them upon wandering in.