Please take a look here to see how proof of existence works:http://www.coindesk.com/how-block-chain-technology-is-working-to-transform-intellectual-property/
You may be stuck in a loop trying to bind an old system to a new one. The horse did not turn into a car. The car replaced the horse.
You're the ones with the claims about the new system (blockchain) being used to represent something that is "old system" namely the legal ownership of automobiles. The ability to prove that a digital document existed at some point in time (as described in the link there) doesn't do anything of the sort.