"why would you ever try and tie WGC physical gold supply/demand numbers to the paper market"?
Because Comex Gold Futures are deliverable.
Anyone who holds a long Comex Gold futures contract and has the money to pay for 100 ounce of gold at the contract price, can take delivery of physical gold one of the three depositories specified in the Comex contract delivery rules. That keeps the "paper" and physical price locked together, whether you like it or not!
WGC data is completely relevant to price action in the futures market.
