This has never happened to me, probably because I don't install the Facebook app and don't give Messenger Lite access to my contacts. If Facebook and Whatsapp were sharing phone numbers or metadata behind the scenes I would expect to see a lot of suggestions when I log in to the Facebook website, but I don't.
Still agree with your opinion, though. Also, I find it annoying that you can't message someone on WhatsApp without adding them to contacts.
Still agree with your opinion, though. Also, I find it annoying that you can't message someone on WhatsApp without adding them to contacts.