> As of today, the integration is fully complete. Users running the most recent versions of WhatsApp on any platform now get full end to end encryption for every message they send and every WhatsApp call they make when communicating with each other

Emphasizing "running the most recent versions of WhatsApp", does this mean the fancy new protocol can still be downgraded to the old one by an older client? I'd save the fanfare for a few more months yet