If there was a zip code that was just virtual PO Boxes, it could use the existing change of address machinery to slap the actual delivery address on when addressed with a virtual box. Assuming they used an entire sectional center facility for it, you could have 100 zip codes, with 6 digits of unique delivery points, so 100 million virtual boxes.

he said "somewhat work the same way". For a person who doesn't care about whether they have to get a new code when they move, the systems are equivalent in their value proposition. Thus is the case for most things that "somewhat work the same way".