I assume the data storage is on a separate chip which - in the context of this attack - is untrusted. That is, the firmware could try to wipe the data storage t

I assume the data storage is on a separate chip which - in the context of this attack - is untrusted. That is, the firmware could try to wipe the data storage too, but that would be relatively easy to bypass and doesn't really gain you anything anyway. Or from the opposite direction: Only the keys are stored within the trusted part of the hardware; they're the only thing you can reliably wipe.