Exactly - and that maximum is the "minimum maximum" across all batches of the device. You might get a particularly resilient one that handles the 10V just fine.

The encryption idea makes way more sense, and the means to short out the cap doesn't even require the device to be powered. The only implementation challenge is that now instead of combining a simple circuit with an off-the-shelf mass storage controller, you need to either find one that can read a key from an external source or roll your own using a micro (maybe this is easy with existing libraries?). But if I was a journalist concerned about such things I'd rather pay a premium for the right solution than worry that the police might be sweating from the heat or that the chip in my drive happened to be especially resilient to overvoltage.