Yes, they did. And yes, like you, it should have been obvious to everyone involved.
Yet for some reason, the Twitter client devs (who had happily shifted all their users to a subscription-only model) all of a sudden realized that they had sold a bunch of one year subs they had sold were going to be useless as soon as Twitter turned off the API and, more pertinent to their pocketbooks, all those customers would be entitled to request and receive a refund through the App Store for their now non-functional app. The devs started whining to their customers about being “small businesses” and having the food snatched out of their families’ mouths and why would anyone be so cruel as to seek a refund?
Christian is showing a hell of a lot more integrity and toughness than the Twitter client authors.