Of course a GPU involves things happening. No amount of using it to describe a brain operating gets you an operating brain, though. It's not doing what a brain does. It's describing it.
(I think this is actually all somewhat tangential to whether LLMs "can think" or whatever, though—but the "well of course they might think because if we could perfectly describe an operating brain, that would also be thinking" line of argument often comes up, and I think it's about as wrong-headed as a thing can possibly be, a kind of deep "confusing the map for the territory" error; see also comments floating around this thread offhandedly claiming that the brain "is just physics"—like, what? That's the cart leading the horse! No! Dead wrong!)