Earlier quoted context omitted.
I do use Signal. But unfortunately I lack convincing power to make everyone else use Signal. But this is not about alternatives to WhatsApp, imo it's weird that this even happens/is possible.
What do you expect from Facebook? They make their money with advertising, of course they will exploit and capitalize everything that gets send through their channels.
I expect that they don't lie on their public website. This is what WhatsApp says on their own website https://faq.whatsapp.com/general/security-and-privacy/answer... :
Neither WhatsApp nor Facebook can read your messages or hear your calls with your friends, family, and co-workers on WhatsApp. Whatever you share, it stays between you. That’s because your personal messages are protected by end-to-end encryption. We will never weaken this security and we clearly label each chat so you know our commitment.