> because I don’t know what the WhatsApp client is really doing with my message. You don't know that the person receiving your signal message hasn't jailbroken

> because I don’t know what the WhatsApp client is really doing with my message. You don't know that the person receiving your signal message hasn't jailbroken their phone and installed spyware unknowingly. When you first message someone using a different platform, Signal could display a warning ~"This contact is using Whatsapp and Signal cannot confirm that communication will be secured, do you wish to continue?"