Messages you write on WhatsApp to someone else are encrypted. It would be unreadable to someone intercepting it.
However, the mechanics of setting up the sending of a message to someone are not encrypted. The route that a messages takes through a network needs to be read by the various servers it passes through and the destination points known. The IP addresses/identifiers of your device or where you are when you send your messages are not encrypted (if you allow your location to be visible).
The data held on WhatsApp servers about traffic flows, your contact groups and frequency of communication, and their locations is valuable and can be shared with others in the FaceBook group.
Signal is supposed to be non-profit making. However, everyone in the group has to download the Signal App.