No. This is obviously not the problem. Nobody at that greeting card company was claiming to be Banksy. The problem is that they are making money off of a Banksy work of art without his permission.
His behavior is quite clearly protecting his financial interests in his own work. That’s actually the only explanation that makes sense. The other option being that he’s opposed to anybody making money off his art, including himself. Nothing he has done in the last year has indicated the latter to be the case.
Sounds like a perfect case for public key cryptography, although it doesn't help with duplicates - but duplicates help his work sell anyway.
Would be interesting to see how it could be applied to something visual that is reproduced in non-pixel perfect ways.
The only comment I have is that I have to fault the article for making a lot of assumptions and leaps to conclusions on Banksy’s intentions, it sort of unilaterally declares that Banksy is selling out and cheating the system.
But what they want is far simpler: they don’t want other people claiming they’re Banksy, and they want to remain anonymous.
The article gets upset at Banksy as a corporate sellout as if they opened up a line of art pieces for sale at Walmart or Target. What Banksy did is more akin to opening up a UPS Store mailbox in order to have an address on file.