I was prepared to disagree with you, but I now have the same interpretation you have. Durable medium can be email - but the example seems a little fuzzy, for instance a durable medium is definitely when the email is stored on a HDD on a customer device. But is it still durable medium if the email only exists in a webmail? Probably yes, but maybe no. So the conservative approach would be to send paper for some things. (Or in this case, stupidly, USB devices. Banks, don't do that, please.)

Ramble Edit: it's unfortunate IMHO that there is no "read only" medium anymore. Not sure what it would look like now when USB-C is taking over the world, and that ship probably sailed, but it would be really cool and useful to have the option of a "data only" USB.

Maybe computers could have one USB port marked as "ROM". Or a switch or LED symbol indicating "ROM safe" mode.

When using such a ROM port, anything USB inserted there would only look like a DVD reader. A USB drive would get its files "mirrored" into a virtual ISO filesystem. Any other devices, such as keyboards etc would be just ignored and not connected to at all.