The reason I started using this pattern is one I didn’t see the article mention:

With legacy style result callbacks, you’ll have both an optional value and an optional error returned - this corresponds to four possible states. If I’m using an API returning this, I have to think about two cases which probably won’t happen (neither an error or value, or both an error and a value). I’d like to think the API I’m using wouldn’t return those states, but since it’s not typed as such then code I’m writing should probably handle those cases gracefully.

By using a result type as per the article, it is well defined that only two states are possible. This pattern is a really nice one, and is a great use of Swift’s associated value enums.