With iMessage, your account isn't (solely) linked to your SIM card. It cannot be, because iMessage also works on devices without SIM cards (iPod Touch, Mac).
I do not think you can claim it fails because it still works after removing the SIM card. You cannot claim that SMS fails on the security front because you can receive SMSes without logging in to iCloud, either.
Comments
With iMessage, your account isn't (solely) linked to your SIM card. It cannot be, because iMessage also works on devices without SIM cards (iPod Touch, Mac).
I do not think you can claim it fails because it still works after removing the SIM card. You cannot claim that SMS fails on the security front because you can receive SMSes without logging in to iCloud, either.
I did not login into his iCloud account. How would I? I did not have his apple id credentials.