correction: it was both! fedbook chat also supported xmpp at first, they never federated but you could at least use it with a jabber client. then when they had enough market share they killed it.
fun semi related fact is that, at least a couple of years ago, was using modified ejabberd (ie an xmpp server) as the backend - so arguably they helped with EEE too.
they could have made their shitty DM system end-to-end encrypt messages by default, instead of burying that feature[0] in chat settings
or, they could have used their MASSIVE wealth and lobbying power to directly fight the warrant in court (if there even was one, they have a long history of just requiring a form ostensibly signed by any cop to turn over private data)
or they could have just lied and said they couldn’t find the data
I don’t disagree that people shouldn’t trust Facebook but saying “they don’t have a choice” is absurd
[0] https://www.facebook.com/help/messenger-app/786613221989782