They still have the capacity to, in this case the experiment is being set up so that a being that COULD pass the test on their own CAN NOT when hooked up to a bunch of equipment.
E.g. Let's imagine we get some cybernetic approach that can work around an inoperable deep brain tumour in the brainstem.
Without the prosthesis the person is in a coma or dead. With it they are normal, but need to be connected to the prosthesis.