Por que o basilisco obedeceu a Tom Riddle (ou a qualquer um)?

Basilisks são controláveis por Parselmouths

The creation of Basilisks has been illegal since medieval times, although the practice is easily concealed by simply removing the chicken egg from beneath the toad when the Department for the Regulation and Control of Magical Creatures comes to call. However, since Basilisks are uncontrollable except by Parselmouths, they are as dangerous to most Dark wizards as to anybody else, and there have been no recorded sightings of Basilisks in Britain for at least four hundred years.
_{Fantastic Beast and Where to Find Them (2001 textbook) - Basilisk}

Parece que as cobras devem ouvir o que lhes é dito em Parselmouth. Por exemplo, no Dueling Club:

Harry wasn't sure what made him do it. He wasn't even aware of deciding to do it. All he knew was that his legs were carrying him forward as though he was on casters and that he had shouted stupidly at the snake, "Leave him alone!" And miraculously — inexplicably — the snake slumped to the floor.
_{Harry Potter and the Chamber of Secrets, Chapter 11}

E quando Tom Riddle diz ao Basilisk para atacar Harry, ele está ordenando a cobra, e a evidência que temos é que as cobras devem obedecer às ordens .