You seem to be assuming that an intelligent organism would have uniform thoughts across their entire body. Cephalopods, at least, don't entirely match that description. Different parts of their bodies act on their own, often with no need for central organization. A larger intelligence could perhaps work like that. Maybe then you would consider just a single section that is still intelligent when severed from the rest to be the "organism" and the rest to be some sort of "colony", but what if the borders aren't clear. What if any cubic meter chunk of alien flesh was sentient, no matter where you cut it from?