[Pseudonymity]

you're over thinking this. The USB does not even necessarily have to be undiscoverable, VeraCrypt is enough. Just put a couple of K on some crypto wallets and hold them in the main volume.

The fact that you've got valuable data on the "boring" volume is enough to explain why it is encrypted.

If you use an amnesic OS that does not right to the USB and is read only on the hidden volume, you won't be racking up the SMART data clocks on write cycles when within the "interesting" volume, making it look completely like a passive USB, sat there looking pretty and gathering dust just holding your wallets.

But even then, you could explain any high usage in the SMART data as it being a random USB you had lying around that you used to use daily, that you decided to throw your wallets on. The SMART data is not timestamped, it's just a total cumulative counter that goes up over the entire life of the device.