Yeah, but you do realize all that you're describing is still more open than "this is a closed app that interops with nobody and also is permanently tied to your phone number", right?
I mean, I don't like the guys and I avoid their services whenever possible, but... man, as an unwilling Whatsapp user the ability to migrate without having to convince all my social circles to do anything but check a checkbox sounds like a huge step forward. I literally surfaced the idea of migrating to the WhatsApp group I thought would be most willing today and got nothing but crickets.