otherwise you risk data LOSS

USB is intelligent. The device should draw as much current as it asks for. If the device is not detecting any host to do any data transfer with, then it is probably idling at lowest unit power load. I would bet it's not bad for it in any way. As long as that power brick lives up to the standard.

That's how it works in general tbf, with a few exceptions like leds
Is that part of the USB standard or just common with many devices?
- It's part of the standard. It's slightly different for each USB verision. USB 2.0 starts at 100mA at 5V and the device can negotiate up to 500mA, if the host can deliver.
- Usb is 5v standard, it can negotiate something else, then it's called usb-pd

Actually that's not as absurd as it seems. NAND memory starts corrupting data if it doesn't get any current for few years. I'm not sure if just power on USB triggers it or does controller on device need to be specifically activated by OS detection. I guess controller goes on the moment it gets power.

In theory, just getting current does nothing. It has to be rewritten. It uses hot electron tunneling.
However, I recently found an mp3-player I hadn't used since longer than 2017 on the bottom of a drawer. It was stored without battery. I put an AAA battery in and it played the stored music just fine.
- Older lithography holds charge longer; the pursuit of more storage at cheaper prices results in engineering sacrifices to make it happen.
NANDalf!
- “No!” cried nandalf, springing to his feet. “With that charger I should have power too great and terrible.
- You shall not pass data!

So, technically flash storage is just electric charge stored in a cell and it does need periodic recharging as the cells leak over time (3+ years minimum). If the flash controller is capable of doing this automatically, then powering the drive like this may enable that to happen. I wouldn't bet on it though.

You wouldnt download a house

gestures at housing prices
If people could download a house they absolutely would.

Oh god this is loss.

My innocent brain wants to know what will actually happen

Nothing at all.
The power supply only puts 5V on the appropriate pins, just like a computer would. Since there is no computer, the drive will do nothing. Even if the power supply has USB-power delivery it won’t actually supply a higher voltage until the device asks for it, and this device won’t.
I don't know for sure but I think if all devices are to spec, nothing happens.

Good advice, but I wouldn't trust Anker with my data refuel after their Eufy scandal

This generations nema 5-15 to rj45 adapter.

/s