Banned third party clients and interoperability. Use their software to access your data on their servers, on their terms, or get shut down. Hard to think of anything more anti-internet freedom. I left when they did that, years ago.

They would not be able to enforce it on desktop computers, short of banning every user one-at-a-time, but they can easily blanket-ban it on mobile phones by requesting Apple and Google remove unauthorized third-party clients from their app stores. (Which they will do. Apple even lists unauthorized clients for services controlled by other parties as against the rules. Whatever that means.)