You can listen to Trey Parker and Matt Stone discuss their research for that episode. There are worse models out there, but this is still a freemium game, something South Park itself lampooned in its episode 'Freemium Isn't Free.' It's less funny because, well, the South Park game has in-app purchases that are, at least to some degree, exploitative and game-breaking.
It's funny that the game is telling you not to play it because in-app purchases can be so exploitative and game-breaking. In-app purchases cost real money and are charged to your account and for those reasons this game should not be played by anyone. To disable the ability to make in-app purchases adjust your device settings. This game contains both in-app purchases and the option to watch ads for rewards.
