I think there’s some confusion about ambiguous endings for complete narratives and cliffhangers for incomplete stories. The first FNAF did not end on a cliffhanger. The primary conflict is resolved. The narrative had satisfactory conclusion to all the characters’ arcs. What comes next is ambiguous, but that’s a new story. The first Spider-Verse ends that way too, as does Empire Strikes Back (though that does a great job of making the question of how the Rebels can regroup so ambiguous it feels like a cliffhanger despite being a complete act). In a boxing match, each round is a complete story; not necessarily the entire match. The whole bout may tell a more complete story, but each round stands alone.
A cliffhanger means the narrative conflict is NOT resolved. Arcs are not complete. Marty McFly still hasn’t made it back to 1985. The Enterprise is in a standoff. The superhero is trapped. The antagonist is still actively engaging the protagonist. In a boxing match, it is cutting away mid-round.
I haven’t seen FNAF2 (I’ll stream it), but I just wanted to comment on this because it is one of the “rules” of writing.