WhatsApp does store metadata in plaintext which makes it susceptible to law enforcement or 3rd parties. The contents of the messages are still end-to-end encrypted; that being said WhatsApp does default to backing up chats in the cloud and those could be subpoenaed by a government.

.. and how easy to frame someone... just keep sending them some messages until they block you.

in the eyes of LE... they have metadata that you spoke with suspected individual :)

And presumably you have a record of those same chats revealing the content was, "I'm not interested in participating in your conspiracy to commit fraud, stop talking to me."

If you meant to imply they could abuse this capability to get a warrant, I'll be concerned about it when they have any trouble getting warrants.