That's because it isn't really generating a weak ETag. From the article:
> You could make the `calculateETag` function format-agnostic, so the hash stays the same if the JSON format changes but the content does not. The current `calculateETag` implementation is susceptible to format changes, and I kept it that way to keep the code shorter.
They seem to agree, a true weak ETag implementation would probably be trickier and require more code :P I'd be fascinated to see how that might work in practice, though.
> You could make the `calculateETag` function format-agnostic, so the hash stays the same if the JSON format changes but the content does not. The current `calculateETag` implementation is susceptible to format changes, and I kept it that way to keep the code shorter.
They seem to agree, a true weak ETag implementation would probably be trickier and require more code :P I'd be fascinated to see how that might work in practice, though.