They want to fly their Gold back home from New York and London. The point is that Frankfurt is no National Gold Treasury hub and if Germany wants to buy or sell its Gold in both Vaults, they just let the amount be moved into another bunker.
I am in aware if Hong Kong has also such a Hub, but the Nations having a slot differs between the two main hubs.
The only reason Washington would take away that Gold would be, from that given perspective, to have Höcke loaded on Cocaine have subsequent speeches about Germany's power in the Bundestag in standing ovations.
We all do consider that unlikely, don't we?