Why Apple was right about iMessage 'fix' for iPhone SMS spoofing

The truth of the matter is that this is not an Apple, an iPhone or an iOS issue at all: it's a SMS issue. The entire SMS text message system has pretty much nothing by way of useful authenticity checking along the way built in, it was never developed as a 'secure' messaging system. You only have to go Google for SMS spoofing sites on the web to discover that there are plenty which provide the service, either for free or for a fee, and the recipient phone handset matters not one jot. As long as the handset itself allows that UDH indicator for the alternative reply-to address to be changed then all bets are off.