I'm not 100% sure who you are replying to, but in my limited experience filling out a manual log-book where we have to write down the diver# seems far more common than photo-copying. So having the short diver# vs the really long card# is quite important.
As for fake cards, I've been told by multiple people who live in Asia that they have seen fakes. The Chinese will forge anything, and if they save $10 per diver cert that doesn't go to the agency...
Sorry, i was replying to Crosshair's comment about counterfeit cards.
I made no assertions about the length of a c card number, only that the qr code appeared to be useless. If you want to verify an ssi c card, you can either dig out the phone, scan the qr code, put in the divers birthdate into the ssi website OR you can log into ssi's website, type in their name and birthdate. The QR code has no advantage that has been brought up or is apparent.
If you want a shorter certification number, use the last 6-8 digits of the card with the best photo.