This is why AI should be on-device.
And I think creating (or mandating) that transparency is probably a precept for offering an alternative product that runs on-device and doesn't have the same trust limitations - because the value prop has to be understood to make it a business. This article may inadvertently bring about a market for "safe translation app for journalists". We need the public to start thinking in these categories if we want a product landscape with both.
Also, when you wrote "precept", did you mean "prerequisite"?
But I don't think "your data never leaves the phone" is something that only journalists and people with similar strong privacy requirements would or should value. All other things being equal, I would always prefer an app that keeps my data local, on principle. The difference being a journalist would make is that I would enforce it, and really journalists should know how to do that. They should be disabling network access, both cellular and wifi (which you can do on Android but I'm not sure you can on iOS) for any app they enter sensitive information into.
Apart from that, I'm assuming that there's an enormous cost sunk into the training of the network. I imagine that alone would make Otter hesitant to let the trained network out of the house, even if it was technically possible.