in reply to 2something

As someone familiar with the XMPP Standards Foundation, I can explain this one 🙂

The answer is rather simple... it's not "finished" yet.

Most clients are on an earlier version of the XEP (0.3.x).

The crypto is 99% the same, but some other things were changed to make the protocol better, more efficient, etc. We need more implementations of the latest version before it can be moved on to "Stable", which is the next stage for XEPs.