“The technology of the last 10 years should have all been open to experimentation by developers without locking users in. There are a lot of developers who believe in this. It's central to the mission of WhatsApp, btw, so if you doubted that it could be lucrative, you should think again.”

WhatsApp has changed and extended their XMPP basis such that it is not even remotely interoperable. They are actively battling third-party implementations. Their server is not federated. How exactly are "open", "experimentation" and "without locking users in" central to WhatsApp's mission?