One reason that doesn't work (among many) is alpha positions in a litter, especially among females, are established only after eight weeks. And hierarchical positions become stable only after eleven weeks. Before then, status changes repeatedly, even top to bottom positions.
Pups are likely rehearsing for roles they'll play as adults. Nobody stays at the top forever. Pack positions change based on who's in the pack.
This is one reason puppy tests aren't very good at predicting aggression or dominance later in life. But by then, we love the dog, and have forgotten what happened in our so-called puppy test, so it doesn't matter.
(P.S. - If you want academic sources for this post, let me know.)