Coexistence enables people with the WhatsApp Business App (not API) to connect with WhatsApp Business Platform, so that messages sent to the app sync with the API (and hence can appear in Missive). This would be a massive unlock for us because it means our sales people can be supported on Missive by a team, whilst they could still directly message clients from their normal WhatsApp Business app. This also means we won't be forced to use templates.