Here’s my take on this.
I can see both sides of the argument for why these apps exist. On one hand, they’re designed for maximum discretion. On the other, that same discretion makes them difficult to identify.
Yes, these apps are real. They often function as a “vault” hidden behind a common icon like a calculator or a simple game. Some are just a facade—the “game” doesn’t actually play and is just a login screen. More sophisticated ones might have a very basic, functional game to make the disguise more convincing. You’d typically access the hidden part by long-pressing an icon or typing a specific code. A good place to start is by looking at app permissions. A simple-looking game that asks for access to contacts, messages, or location services is a potential red flag.