This obviously sounds like something that could be possible, but equally possible is that there is no banksy and it is simply a marketing tactic, where banksy was originally one person that evolved into random artworks from many people.
Given how it started I think this is BS. He was a graffiti artist who got a lot of recognition, it wasn't an art/marketing scam because if it was the recognition would have come a lot faster.
I'm happy he is selling his work to people for lots of money, they are idiots for buying it, doesnt mean the works aren't good, but they are still idiots.