A promo, aftermovie, recap and Reel can use the same source footage, but they do not do the same job. The difference is not only duration. It is what the viewer should understand or feel.
A promo sells one clear idea
A promo should quickly explain what is being offered, who it is for and why it deserves attention. It can be atmospheric, but the main point cannot disappear behind mood.
An aftermovie brings back the feeling
An aftermovie does not need to report every hour in order. It compresses the people, place, energy and strongest moments into a film with its own arc. Someone who was not there should still understand why the event mattered.
A recap gives an overview
A recap is more factual. It works when the audience needs to see what happened, who took part and which programme points mattered. Statements, labels and a clearer chronology often belong here.
A Reel or Short needs one focus
A short vertical video usually needs one scene, idea or reaction. It does not have to explain the entire event. Three precise Reels are often more useful than one thirty-second cut trying to contain everything.
The format should follow the goal, not the label that happens to be popular. One set of footage can reasonably produce a master, a shorter version and several focused social cuts.