Because they made something different with the same process, instead of making the same thing with a different process. Feature size didn’t get any smaller. (or, rather, you get the order of magnitude improvement without it, and those gains were vastly more than the feature size improvements over that time period)

Also because “process improvement” usually refers to things where you get incremental improvements basically for free as each new generation of fab rolls out. Unless you can invent a 4D flash, this is a single (huge) improvement that’s mostly played out.

> with the same process

Same process node.

Node is part of process, but all the layering and etching techniques they figured out to make 3D cells are also process. At least that's how I see it.

Oh well, I don't want to argue definitions, I just want to clarify what I meant.