Lyxen
Great Old One
Story-oriented play may view prepared notes as ideas and potentials, and not sacrosanct - they could be ignored, added to, or edited on the fly as needed.
I honestly think it rather disconcerting (but I will put this down to the nature of internet discussion) that some people can on the one hand totally want sandbox playing which requires the DM to improvise a lot and at the same time absolutely want him to stick to what he prepared.
But if he did not prepare anything, as he is improvising to cover the sandbox aspects of the game, how can he stick to what he prepared ?
That's the reason I stopped the discussion about using devious tools for DMing. Of course, I would not advocate using them for a, as you said "tactical & wargame" type of game, it would totally devaluate what the players are trying to achieve, which is a sense playing against the DM or at least against the situation that he has set up, so I agree it requires honesty (and on both sides).
But as you go into more story-oriented play, especially if you have a lot of intrigue, and therefore a lot of improvisation (another characteristic of that kind of game is that it goes much faster because there is much fewer combat, so you get much much faster into unknown territory leading to improvisation), I'm sorry, but these devious tools become critical and almost a necessity.
And I'm sorry, but this is not bad DMing, in any way shape or form because by stepping into that kind of game (actually by wanting it) the players agree that these tools might be used, when necessary. How else can the DM play all the evil geniuses keeping track of their plots ? Are you all evil geniuses able to run all the intrigues in parallel ?
So deviousness becomes necessary, in particular metagaming about hearing what the PCs are planning to do and retroactively creating the plots that make these ideas into interesting storylines (and, by the way, there is not even a hint of cheating there, as nothing was pre-prepared, so even that spurious claim cannot be used). Again, like a stage magician, everyone expects that there are going to be tricks when necessary, they just don't know which ones, and they actually don't care as long as the story and intrigues are cool and epic.
And it comes back to trusting your DM, and knowing that he is not playing against you. Because, honestly, that is the part that is the most sad about all those stories, at the core of it, there is a mistrust between the players and the DM, and the players feel that they need to protect their agency against a nasty DM who is only out there to steal it and deprive them of their choices (and what makes it even worse for me is that these players, on the other hand, think that it's totally their right to steal the DM's agency and to ask him to run whatever their fancy switches to, taking into account none of his prepared work, own thoughts and desires, and even less his capabilities, I'll come back down to this in another post).
I really hope that someday, you can play with a DM that you can fully trust and that you can enjoy that kind of game in a fully collaborative mode. It's by far my preferred style of play, our groups have been doing it for many decades now, and there's never been a problem of trust around this, because actually, you know what, we love our sneaky DMs who can pull amazing plots out of the air to make our characters shine.