Exactly. E2EE is just "transit encryption" when clients are not open source/ audited/ trusted. And FB cannot be trusted (I'm not going to list instances by which they gained my distrust here).

Encrypting metadata is also really hard. See the Matrix (and XMPP) community for detailed discussions on why that is.

I use and advise others to use E2EE encrypting tools, all are open source, audited and popular.

Fake sense of safety is worse than understood unsafety.