You're out of your mind if you think the regular guy off the street should:
Know the difference between IMAP and POP3
Know the inner workings of iMessage
If Apple requires proof of understanding to sell their tech, they should submit users to a test. Otherwise, their tech should work how the users expect it to. And deleting messages when I press the damn "delete" button is how any sane person expects things to work. Now, if Apple wants to make a copy and store it in their asshole, and I have to penetrate them anally to delete it as well? That's fucking debatable in court if it's a reasonable expectation for a user to have.