It's a hard drive. The storage is persistent. Assuming your argument is that the world the device is constructed in isn't guaranteed to be persistent, then that renders physical hard drives in our physical world as non-persistent; let's see how persistent our data is when Sol goes red giant... ;-)
jeremycole is correct, its closest real world analogy is a bubble memory or the short lived fad of using CCDs as a large linear memory (that went nowhere around the mid 80s) or most accurately its compared to an ancient mercury delay line (although Hg delay lines and CCDs are/were not persistent but their mechanical operation is similar)
There was a fad of endless loop tapes in the 80s... Exatron stringy-floppy. That is probably the closest physical analogy. Think "cassette tape interface" with electrically controllable R/W on an answering machine cassette, all conceptually of course this isn't how it actually worked. It had nothing to do with a floppy other than storing about the same amount of data, very java vs javascript like.
It's a sign of the times. "Hard drive" has come to mean simply "nonvolatile local storage." Some people who know better even talk about "SSD hard drives" without snark or irony.
It wasn't that long ago that "hard disk" meant "3.5 inch floppy disk" to many people. Pedantically speaking, they were wrong, too, but the little floppies were hard to the touch and they did store files. It made sense.
It's a triumph, in a sense, that so many people are at least able to grasp the function of this invisible machine (the hard drive) even if they aren't using the term in an engineer's excruciatingly precise and correct way.