I do believe that "future prologue" is actually a well-known term, since I did find it by googling and I read about it in a book.
Right now, both of your examples read like a future prologue. It's more like the monologue one is more character-focused, and what you showed for a future prologue is action-oriented. In your example of the monologue, you set up that the story will be about the character getting the honor of supreme command, so the reader will be interested in that story.
To me, it seems more like a question of writing style. Like I said, in your example of monologue, the style is focused more on the character. In the other one, it's focused more on the action of the battle. So the answer would be more about the story that you want to write.
Since you picked the more character-focused one, it'll be great to see the rest of your story written that way. Quite a few trainer fics tend to brush over the characterization of everyone and are much more action, getting the story done as fast as possible. Your choice has already started the distinction of your fic compared to others, and I'm looking forward to seeing what else you come up with.