Well, that's a telling finding. It's just "telling" different conclusions about "global wealth", "JPMorgan's market capitalization", and gold's "fair" value to different minds ;)
The only thing that's safe to assess about that bullion is that for all human intents and purposes, it'll outlast infinite numbers of generations, and the other stuff --- won't. That alone tells of the impossibility and futility of putting any sort of currency number on it, in fact, any figure will do --- $100 or $100k, whatever the world perceives will be equally valid and equally workable. Doubly so since "you can't eat it", it's in the final consequence not broadly "needed at any price" for industry, and the actual supply for its prime purpose (preserve some proxy of wealth through the generations) need not be increased, and every physical ounce above or below ground is in extremis already owned by someone.