Well, it's possible that the Final Boss met an unexpected fate due to a twist in the plot or a hidden power of the hero. Maybe there was a sacrifice involved or a strategic alliance that led to their downfall.
It could be that Chapter 7 has complex storylines that need a recap for better understanding. Or it might be a way to refresh players' memories if there's been a gap in their gameplay.
Well, it's not really about age. It's more about the characters' feelings and circumstances. Some manhwas might challenge the idea of age and focus on true emotions instead.