I knew a guy that used deep packet inspection in a service[1]. He told me that back in ~2016, when using WhatsApp, the text was encrypted but nothing else was. If you sent a picture, it was in clear text.
I don't know if this is still true, but because of this, I have serious doubts about anything security related coming out of FB.
[1] Being intentionally vague here as to not dox him.
WhatsApp was/is heavily scrutinized, and it's fairly easy to sniff your own network traffic. It's unlikely that "some guy" and no one else discovered that WhatsApp was not encrypting content.
I don't know if this is still true, but because of this, I have serious doubts about anything security related coming out of FB.
[1] Being intentionally vague here as to not dox him.