I've noticed the numbers, never thought they meant much of anything - especially as it's not the same across brands.

We mostly eat Delalo pasta (grown / made in Puglia). In the interest of maybe solving a puzzle, I pulled a few out of the pantry, and here are Delalo's numbers:
Capellini 01
Orzo 65
Radiatori 42
Cavatappi 67
Fusili 27
It doesn't seem to be related to thickness or cooking time. I think you're right on the numbers being die identifiers.
Also, if I *had* to pick a supermarket pasta, DeCecco is much better than Barilla, but not up to the store brand 'imported from Italy' boxed pasta (pretty sure it's Bionature, from Bologna, not sure where they get their wheat, prob somewhere in Italy).