They no longer accept world records for not sleeping because the record breakers have universally suffered lifelong cognitive damage.

We know more generally that people who get decreased amount of sleep suffer increased rates of physical and mental health issues.

It is not a very big leap from "causes permanent damage" to "enough permanent damage can cause death" and of course, keeping someone awake until they are hurt or killed is deeply unethical, so even if it could be proven in other species, you'd still be here arguing that 'they aren't humans".