I think it's slightly different in that it changed though. A 16gb iPhone always meant that there was a 16gb storage module inside the device and then some of it was used for the OS (how much of it has varied over time however, which I agree is a problem)

In the sandisk case, at least from what I understand, it that 16Gb used to mean like a 17Gb module, with 1Gb used for system functions, now it's a 16Gb module with 1Gb used for system functions

Since there are no 17 GB modules (to my knowledge), they would have had to combine modules of different sizes. The f3 output in the article also states 16 GB for both drives. The old drive already only exposed 14.9 GB (GiB) of usable space. So it seems to me that is is only a quantitative change, not a qualitative one.

Phones are actually worse in that a mere OS update can decrease the amount of free space, which is something that presumably does not happen with USB drive firmware updates.

Are all the sizes really that even? Despite weird layer counts and stacking counts and typically doing 3 bits per cell?

Still, a 16GiB module would be 17 billion bytes. No need to combine different sizes. Unless you're saying a single module would have a decimal capacity?

If you take a 16GiB module and sell it as 16 billion bytes then that gives you 7% overprovisioning. Overprovisioning 10% would give you a 15.4 billion byte drive. If you want 16GiB then it's a quantitative change of how much you lose. But if you go by their promise of 16 billion bytes then it's a qualitative change that they broke the promise.