[nousermane]

Unlike RAM, where you always get exact power-of-2 number of bits per chip, modern flash storage normally ships with defects, plus error-correction codes to deal with those.

Number of defects vary. Chips coming from the same factory, even same batch, are likely to have different number of defects, and will be binned accordingly.

Devices with larger (but manageable) number of defects will simply have larger ECC region reserved - leaving smaller space to show to host computer. OP's new USB stick is like that, that's it, I reckon.

[exmadscientist]

There's more going on here: the read and write times have also changed. This looks like a completely new hardware spin. And I'd bet it's got TLC flash now instead of MLC, or something of that sort.

I hate TLC. But at least it's not QLC.

[fomine3]

General trick is to have NAND chips in GiB and sell product as GB. So difference 16GiB - 16GB = 1.1GiB can be used to management area / wear leveling.