Ah, yeah, I could see how that might help if it's robbers trying to get your bank pw/wallet key.

I think it's more for Chinese communist police raiding her home. Since she runs mains voltage through the USB drive the thing would have to be plugged in.

wouldn't the act of destroying the drive be enough to convict anyway?

Yes, but they could not, for instance get data on or conversations I've had with other people and go after them. A firestop of sorts. It's far from a universal solution, just a very low tech, very theatrical option for very specific threat models