I get the arguments for this idea. Why did USSR play along? They (claim they) had all the same transmissions and everything else we did, and they called us to congratulate us. I guess they could have just made a wild guess, but it seems more likely that they ... observed us land on the moon before calling us to congratulate us on landing on the moon.
Likewise we observed all their unmanned flights, and our records for all this agree.
Kind of hard to hide Saturn V launches. That’s why there genuinely haven’t been any since 1973.