Does this mean it’s trivial to spoof iMessage from arbitrary phone numbers not already registered with iMessage, or hijack any non-iPhone users SMS messages by tricking the iPhones they communicate with to send replies via iMessage to the spoofer rather than SMS? If this is true, (edit: probably not true,) and I’m just speculating without specific knowledge, it seems Apple would shut this down for legitimate security reasons, and perhaps re-engineer things to prevent this.