No thats actually a great argument.
The results can be inconclusive, but only when the participants fail. The man walks infront of the mirror and pays it little attention. Now this does not mean the man isnt self-aware. So here the results would be inconclusive.
However the woman gets infront of the mirror and brushes her hair, and puts on makeup. Typical human grooming behavior, so in this case it can be concluded that the woman is self-aware.
Therefor the test was useful in proving the woman's awareness even if not useful in proving or disproving the mans.