The reality is that RNG-based games use mathematics and paytables to determine what a game will pay out over time, even in a bonus. A pre-determined bonus will pay a certain amount over time. As players, we can't know what changing our timing can actually do on an RNG machine. A common way for slot makers to report that a given picking bonus is not predetermined is to display unchosen options when a bonus ends.
Village People Party, for example, has 38 albums you can choose from, 9 of which are party spoilers. The important thing to remember is that the results are really random. The game doesn't work cyclically, and slot machine jackpots don't expire. Slot machines don't get hot or cold either.
It only seems so, and only then in retrospect. It's not something you can predict, any more than you can predict with certainty what the next card will be when you deal a deck of cards. What I think is that they use a rng, so they are random, but as soon as you hit spin, the result is decided that the reels are just an image to show a win. That's why some games show a win before the bonus ends.
I could be completely wrong though lol.