The thing about the flashback mechanic is that it is very heavily a genre convention and is about as appropriate to other genres as wizards getting to cast fireballs is appropriate to most genres. The only two and a half games I can think of with it (Leverage and Blades in the Dark with the half being some Fate settings) are very explicitly heist games. And if you watch almost any heist movie or series (such as Ocean's X or Leverage, the latter of which was licensed for the game) then you frequently see flashback scenes where the flashback explains what was really going on and how although our characters appear to be up the proverbial creek without a paddle instead that's just how they want to look to the bad guy.
The flashback mechanic is in some ways meta because it's doing things out of chronological order for the characters. But it's doing things in exactly the same order you'd see it if you watched a show or a movie of what the characters did. Is it authoring? In the same way that casting disintegrate (or even fly) to eliminate problems is, yes. But it's entirely expected for the genre and if I want to play a heist game that doesn't take ridiculous amounts of time in planning it's the best way to do it.
Flashbacks, in the sense of whole scenes recounting how a certain plan was made or a certain contingency anticipated, are - I agree - a heist movie thing.
But here is a weaker/looser sense of "flashback", in the sense of an appeal to past character experiences to explain something that occurs in the "present" of gameplay:
Gygax's DMG, p 20 This ability assumes that the language is, in fact, one which the thief has encountered sometime in the past. Ancient and strange languages (those you, as DM, have previously designated as such) are always totally unreadable. (Gygax's DMG, p 20)
The move from this mechanic - where a failure seems potentially to imply something about what the PC
doesn't or
can't remember - to a Wises check in Burning Wheel - where a failure might have a similar implication, and where a
failure success establishes something that the character does remember - is not a massive one.
There is the caveat about languages deemed by the GM as unreadable. It reminds me of the caveat on the Apocalypse World move
open your brain (AW p 88):
When you open your brain to the world’s psychic maelstrom, roll+weird. On a hit, the MC will tell you something new and interesting about the current situation, and might ask you a question or two; answer them. On a 10+, the MC will give you good detail. On a 7–9, the MC will give you an impression. If you already know all there is to know, the MC will tell you that.
On p 204, Vincent Baker adds the following commentary/advice: 'The “you already know all there is to know” clause is there, but I’ve never used it and I hope you never do too.' In other words, there is an issue here of GMing ethos/agenda. Gygax's advice is oriented towards the possibility that the GM will have "secrets" from the players, or puzzles that the players can't gain answers to by deploying ordinary abilities (eg an ancient and strange language will need magic rather than just a thief or assassin to read it). Whereas Baker's advice is oriented towards "playing to find out" and the idea of the fiction "snowballing" as the players declare their PCs' actions.
I think it's fairly obvious that Gygax's ethos is oriented towards the GM maintaining a high degree of agency in respect of the shared fiction, whereas Baker's ethos is oriented towards letting the players take much of the lead in this respect.