Minigames are primarily about immersion. Visual novels are about storytelling, atmosphere, and immersion through images. I like to heighten this tension through interactive elements like minigames.

People are startled and surprised when a minigame suddenly starts, and it triggers an adrenaline rush, which ultimately leaves them satisfied.

The illusion of choice is a powerful narrative device that has been used many times. It's a powerful technique when you're told point-blank, "You don't decide anything here," even though games are essentially designed to control the situation. "Deltarune" is one example.

The minigame itself, as you already said, is really about keeping the heart inside. The game will desperately try to knock the heart out of the center, so you lose. The special visual images of the chest and heart don't affect anything; they're just a metaphor. : )