There might be some things that we don’t want the other side to know we know.
Russia and China have had UFO/alien secrets for many decades.
They know...
Everything.
As closed societies they do not share.
As an allegedly open but in fact closed society we do not share either.
UFO/Russia history:
https://www.amazon.com/Case-Files-Russia-Philip-Mantle/dp/1907126031
https://www.amazon.com/UFO-Chronicles-Soviet-Union-Samizdat/dp/0345373960
UFO/China history:
https://www.amazon.com/UFOs-Modern-China-Wendelle-Stevens/dp/0960855831