Considering that literally millions of people play the game this way, it is demonstrably untrue.
Some people sit down at tables and tell stories, I do not deny this. Are they
gaming? That seems to be rather a different question.
When one person, as you have said, has
literally unlimited power, and actually uses it to manipulate the world in ways that DO affect the players, but which the players are never allowed to know about, which will be hidden from them, and which will be denied if questioned, how exactly can you be
gaming? You're certainly witnessing a fictional world, I have never questioned that. But poor play will be corrected and good play will be countered. That's not gameplay; that's being taken for a ride.
Sure. But it seems that at least in this instance the on-true-wayism comes from you.
Is it? You're the one who is claiming people HAVE to be able to deceive their players--not just have characters that tell lies, but actively pretend that they never make mistakes.
The numerous passages that outline the GM power both in the PHB and DMG have been quoted to you in previous discussions on this topic, and you have participated. I am not going to do this again, but I'll remind you that DMG literally advises how to fudge dice.
I'm aware of what the 5e DMG says. I am also aware that
it's one of the things that says that players react badly to these tactics.
It is not a secret. It is in the rulebooks that the GM can do this. That the flow of the game is not constantly interrupted to give running commentary on GM's decision making process is not a deception.
So you tell your players you're fudging the dice? You have made it explicitly clear to them that any results you don't like, you're going to eliminate and replace with ones you do like?
Because that's what you're saying here. And that's what I'm opposed to. Anything you can do with deception--even "fixing" an encounter that has gone completely pear-shaped, even "adjusting" a monster that doesn't fit, even adding new creatures or eliminating excess creatures--
literally anything you can do with deception, you can do without it.
Why, then, should we do it if it has even potential negatives that cannot even in principle be present if we avoid deception? Why is deception necessary when it at least
could cause problems (and almost everyone agrees
will cause various problems if any use of deception gets revealed to the players), if there are non-deceptive methods that get all of the same results?
This insistence that you have an absolute right to deceive your players whenever you feel like it--
that's what sounds one-true-wayist to me. It's clearly a problem for a large chunk of players. If it weren't, you wouldn't see nearly every discussion of it explicitly warn to never let your players find out. And if it
is a problem for lots of players, why not just...not? It's not any harder. You don't lose out on anything you could do without it. You don't take any additional risks by avoiding it.
What is gained from deceptive techniques?
I have reskinned a monster, the players are fighting it. Then they hit it with a spell. At that point I realise the statblock lists resistance to that type of damage, but that resistance really makes no sense for what the reskin is representing. So I ignore the resistance and let the spell to do full damage.
Is that simply an error--as in, you were
going to remove that, you knew that it should be removed, the players are aware that that thing shouldn't be there, and it just happens to be there because you, personally, just didn't remove it?
In that case--and literally ONLY that case--I might tolerate such a change, but it should still be noted. "Oops, forgot this thing
shouldn't have fire resist. That's getting ignored, I assume you guys are okay with that." (I would expect chuckles and/or sarcastic "oh noooo" responses to that at most tables.)
Changing HP? AC? Turning crits into misses or misses into hits? You're either taking away players success or removing the cost of player failure.
I will grant you one thing. You have, in fact, actually managed to generate a case where a change to a monster statistics is warranted, purely because it is a clerical error and for literally no other reason. That's something I hadn't seen before.
But if it's anything other than a clerical error--and I really do mean that it needs to be a clerical error, as in, you actually did
build it wrong, including something that should not be there
at all, not just
realizing later that you made a fight that was harder than the party could handle--then the limits of DM power still apply. Changes should be justified if they are going to happen at all. That justification can be as simple as "you don't
know why this changed...but you probably want to go find out." (Hence why I say, even
without prep, there's never anything you can do with deception that you
can't do without deception.) But it needs to be
something--or at least a real, reasonable chance to find out, even if the players don't take up that chance, or do take it up but fail to make good on it (e.g. bad rolls, looking in the wrong places, not considering the question, etc.) Players have the responsibility to go looking for answers; DMs have the responsibility to actually have answers, and make them truly find-able, not buried so deep no one would ever actually find them.