Also you have the physical money and don't rely on computers or similar. More secure (if you ignore Die Hard 3).
If countries start moving the gold away it's a) sign that they need the money elsewhere or b) they don't trust the current location anymore.
It is plausible to me that building up a gold reserve might be worth it, longterm, purely because the gained trust/perceived stability nets you slightly better conditions when financing megaprojects alone (like the Fehmarn tunnel): Over a few centuries you might save tax dollars thanks to investing into bigger gold reserves earlier.
And gold is objectively useful if things go to shit-- just look at Russia for a recent example-- gold is nice for mitigating sanctions and stabilizing your currency under bad conditions.
II World War hasn't started with German attacking Poland 1.IX.1939 and Russia (Soviet Union) on 17.IX.1939. There was Spanish Civil War earlier (1936), annexation of the Sudetenland - part of Czechoslovakia in 1938.