You trust the holder of the Bullion or I guess https://www.anthemvault.com/ in this case, so the difference between a piece of paper that gives you ownership of the gold would really be that you can purchase/exchange it via. a Blockchain transaction.

I'm not sure you get any advantage from the Blockchain in this case though, you still have to trust a single-party, and their local government may still require all kinds of identifying information for regulations sake from this single-party.

Further the article doesn't specify which Blockchain they are using (neither does their website)? All of the extant Blockchains aside from Bitcoin are prone to various security problems.