Typically, the decisions about who lives, who dies, and who tells the story in an animatic are made by the team of writers and animators. They consider various factors such as character arcs, the overall theme, and the intended impact on the audience.
The Hunter x Hunter manga is unfortunately not complete. The author has faced various issues that have led to intermittent breaks and an unresolved storyline.
The Hunter x Hunter manga has indeed concluded. However, the ending might have left some fans wanting more or with mixed feelings depending on their expectations.