When the roll says fail and yet you narrate success anyway, what was the point of the roll?
Well, all I can say is, I never do this. On exceedingly rare occasions, I may reflect and realize "y'know what, I never should have asked for a roll there in the first place", and when I realize that, I tell my players so. It's not something I do lightly, but I also don't do it secretly either. I just tell my players what's on my mind and we talk it out.
Or was success always guaranteed and the roll merely to determine degree of success? If yes, I get it, but wouldn't that be somehow mentioned to the players up front, as in "Getting up won't be a problem but time is crucial: you'll need to roll to see how long the climb takes"?
For me, this isn't a matter of a roll regarding guaranteed success but changing the degree thereof. We simply don't roll with regard to
whether the climb will succeed or not. That will happen. The player already knows this. Instead, the locus of failure-vs-success is specifically in, as you say, the timing. That's still quite obviously a failure on one side (you were too slow, the enemy got away) and a success on the other (you were fast enough and can
do something before the enemy gets away). That's something where both success and failure are interesting. With success, the players push closer to a resolution right now, whatever that resolution may be. Merely finishing the climb does not resolve the conflict (most of the time, I suppose there could be some very strange circumstance where that's not true but outside of highly contrived circumstances I just don't see that happening), but it will push things to a rapid end, whatever that end might be. Conversely, with failure, the players now have to resolve a different kind of problem: their quarry has escaped, they need to find them and track them down. That's a new conflict, and replaces the high-temperature tension with a low-simmer tension.
(
@EzekielRaiden recently gave me a bad time for suggesting the reverse, where failure is guaranteed and the roll is to determine what that failure looked like and-or caused).
Yes--because I don't think that there should be a roll for that purpose.
But we certainly can have rolls, which are themselves genuinely about success vs failure,
separate from this already-failed thing. "You cannot stop the collision. That will happen no matter what. What do you do, Captain Smith?" can be answered with "I'm desperately thinking about how to minimize the damage. As part of my training for this voyage, I remember specifically studying the plans and layout of the ship." At which point, DW would have a Spout Lore roll; assuming a success, the player learns something interesting
and useful, which in this case would probably have been "damage to the
side of the ship is actually much more dangerous than damage to the
front" and thus Smith decides to steer into a head-on collision at the slowest speed they can manage, unlike our timeline where a devastatingly foolish decision was made instead.
(Ironically, I used "Smith" as just a filler name, but it turns out the actual captain of the Titanic was named Edward Smith.)
I don't see it as conservative to not want to undermine the integrity of my own game.
The problem is your stubborn determination that this approach
must always be "undermining the integrity of the game", rather than...y'know, being open to the possibility that you've misunderstood something, and that the technique
does not actually do that. "This newfangled technique OBVIOUSLY must ALWAYS undermine the integrity of the game", particularly when numerous people have specifically gone over how your mistaken understanding is mistaken and have reiterated that the alleged fault you see (various versions of "it isn't actually failure"), is very much an example of unnecessary and counterproductive conservatism in the space of game design.