The only part of this story I have a problem with is "decided to actually build the feature -- even though the app was never designed to support that format". Yeah, no shit, if the app was designed to support that format, he wouldn't have to build the feature because it would already be there. That's not an "even though", it's literally a requirement for it to happen. Author, editor, or whoever completely fails not only at basic English, but at logic, too.
But, this is also a hilariously simple feature. It's a format conversion! What the app already does is orders of magnitude more difficult, and the new feature can almost certainly use existing code to do most of the job. The output part already exists, this is only a new input part, and immensely simpler than the existing input part. This doesn't make it not news, of course.
Finally, the answer to the dev's question "Should we really be developing features in response to misinformation?" is "why not"? There is not a single solitary reason not to do so. And, to close the circle, he could not have developed features which people said did exist, because they would already have been developed. But even more accurately, he did not develop the feature in response to misinformation. He did it in response to demand, or put another way, the customer response to misinformation.