I had no intentional of "fooling" you. Look a few messages back. I quoted your wording verbatim. I didn't see it necessary to do that yet again.
Your Blackberry example is different, because your friend completely disabled texting. Of course he won't get texts. Despite what you wrote, "if an iPhone user has MMS disabled, MMS cannot be sent or received," no one is talking about that case. Of course that happens if you switch testing off completely.
I'll spell out the iPhone case I described earlier. The user has the following settings:
Send as SMS: ON
MMS Messaging: ON
Group Messaging: ON
Show Subject Field: either OFF or ON
Now if someone sends an MMS to this user with data off, nothing happens.
Blocking these MMS messages is stupid, but if AT&T and Apple really want that to be the behavior with no notifications, then the setting interface is incorrect. If the user turns off data or has no data plan, then the MMS setting should be unavailable and forced to OFF. The user shouldn't be able to turn it on.
And since you like to compare to other carriers, yes there are other carriers that allow MMS with no data plan on a smart phone. For example even very new cheap ones like Lumia 521 can be configured to do this on T-Mobile. On AT&T with the Lumia 520, you can receive the MMS but get an alert to enable data if the incoming message includes a picture attachment. So yes it's an iPhone limitation. It is not "all smart phones" as you imply it is.