Earlier quoted context omitted.
You think Facebook does not have access to Whatsapp messages ? Would be very surprised if thats not the case.
Facebook doesn't have access to WhatsApp messages. WhatsApp uses the same end-to-end encryption protocol as Signal. We know this is true because the app has been extensively reverse engineered to create these third party clients among other reasons.
Everything is closed source, and you have no idea what is running on their servers, etc, so all your suppositions are worth basically nothing.