No flips for you!
You shifted the pea, again, from expecting a solution to the challenge to having prep available for possible things. There's a difference between having a stat block on hand if a fight breaks out and planning a challenge to be a fight. The latter will lead you to presentations that push towards a fight, the former is just ready if the players decide to have a fight.I don't see it that way, though the thinking you describe is how some GMs approach it, especially with combat encounters. But I merely see it having prepared certain mechanically somewhat more involved things in advance. Like if there is a situation where combat might ensue, then it probably is the best to have the stats of those creatures at hand instead of scrambling to find (or write!) them when it turns out that the characters decide to solve the issue with swords. Being prepared allows the situation proceed smoothly, the suspenseful and tense escalation of hostility directly leading to the combat without being interrupted by the GM having to sort out the mechanical details. Same with many of the more complex skill usage mechanics being discussed in this thread, having the the framework ready will help. And sure, you cannot be prepared for everything and more importantly you shouldn't be fixated on what you planned having to happen. My favourite moments are when the players resolve a problem in some utterly surprising and unexpected manner. So yeah, again, you can do both, be prepared and be flexible; these things don't need to be enemies.