>I think, if someone is holding down both the accelerator and brakes
...which is not something that happened in this case in any way, as far as we know.
According to Tesla, "due to the terrain the accelerator may or may not disengage when the brake is depressed".
Not "due to the driver holding down both pedals", but "due to the terrain".
(The driver clearly says that he was not holding down both pedals, too).