1. Apple makes it clear that this indicates whether someone has an iPhone. This does not make clear to non-technical users that this indicates that you are sending a different type of less-secure message to these users.

2. Even if Apple made this clear, it still creates a pretty insecure environment in practice. If you don't know ahead of time what phone someone you're talking to has, you must receive a message from someone before you can know whether messages you have sent them are secure, in the same chat application you use to send secure messages