>Majority of people I talk to are Messenger, [...]
>The issue is, I have only 3 chats happening in WhatsApp in the last 2 years that are non-business chats. And all 3 have had conversations resulting in advertising.
you realize that Messenger is owned by facebook? I find it baffling that you think the leak must be from whatsapp, when in reality both Messenger and whatsapp are both owned by facebook.