The travel forms to visit the US ask if people have ever been involved in espionage, at least they did, I'm not aware that it's changed.
You can guarantee the many people who work for intelligence agencies of US allies aren't admitting to that when they travel to the US.
It's all a bit of a game.
But they're required by laws of their own country to lie, presumably. There are certainly game-like aspects.
Those forms also ask if you've ever been a member of a communist party, and basically everyone over 35 in all of Eastern Europe would have to check that one (they don't, if they want to enter the US)
"Do you seek to engage in or have you ever engaged in terrorist activities, espionage, sabotage, or genocide?"
Quite.
The reasoning for some of these questions is that if you are caught, it’s sometimes easier to charge you with fraud (lying on the form) than the actual thing (such as espionage).