What they did was suddenly yank access for a handful of apps then go silent for four days, before sending an email out to API users for (maybe?) a new program which we can’t be 100% sure was part of the plan or just an old scheduled mailer by a now-fired person. We are left guessing because nobody really knows what’s going on at Twitter any more.
If you were subscribed to a free service and they released a paid version, would your choice of paying be affected by the fact that your free account was removed without warning?
What if you had built a business on the free account; would the sudden shutdown of your business affect your decision to build a new project on top of the paid product?
Monetization requires users trusting you enough to pay, eroding lack of trust as you reveal your paid product is a mountain sized red flag.
An easy win-win-win-win for Twitter, partners, users and developers.