Tests like this are intended to prove or refine information derived from clues from damaged subjects. You can learn a lot of things about complex systems like the brain by studying their failure modes, but you have to be careful of inferring causation from correlation and other such fallacies — for instance here they could have been trying to rule out the behaviour being a secondary symptom (the correct response actually being controlled elsewhere normally, but that is blocked by the damage rather than the damage having affected it more directly), or testing to see if multiple areas are directly involved in the behaviour rather than it being as simple as that one area seeming to control the veto, or just ruling out a pre-existing condition in the initial subjects unrelated to the subsequent damage.