No, xmpp and simplex do not leak metadata.
The header of XMPP-Messages are unencrpyted, A Spyserver in the net can easily collect all the data, that fly´s by! SimpleX collects IP-Adresses and is connected to Big Data Companys - see Messenger list. 85% of all Smartphone run on Google Android, which sends encrypted data to Google, everyday. So Google knows nearly every User PLUS its IP-Adress.