This is not a bug, it’s intended behavior, even if it’s counterintuitive and unlike how most other apps and games work.
You don’t choose your answer by selecting it directly on the screen but by swiping on your Apple TV remote’s touch pad in the direction of the answer. If your choice is to the left, you swipe left, if’s it’s the bottom one, you swipe down etc.
This way, if you’re playing local multiplayer, your opponents won’t be able to see your choice, even if they look at the TV screen, until the correct answer is revealed.
Took me a little while to figure out too, but it kind of makes sense. The app should communicate this way of control much more clearly.