Warning: Long post ahead - the following post is meant to open a conversation between myself and someone who holds opinions I do not agree with so that I might gain understanding of their opinion. It may seem written by an arrogant and pompous person, which is not necessarily intended on my part but is inevitable when a table-top gamer states clear and vehement disagreement with Gary Gygax on principle matters of Dungeon Master etiquette.
Not to say you're wrong doing what you do for the reasons that you do it
Thank you for that courtesy that most people I have encountered across the internet do not extend.
in a game where the GM creates the challenges to throw at the players, it can happen that you mis-judge an encounter at the design stage.
Which is, in practice, no different than intentionally designing an encounter that is intentionally too-difficult or inconsequentially easy - both of which are perfectly fine practices and encourage event resolution other than direct combat.
It's certainly not cheating to say to yourself "whoa, this minor obstacle has turned out to be more deadly than I intended -- let's dial it back...". Whether dialing it back is fudging some rolls, or adjusting numbers on the fly is the same thing: you're being fair.
I reject that definition of fair - I prefer to define "fair" as being in accordance with rules and standards.
That means that any change not being made as a permanent alteration to the rules (which I only make as a committee with my players) is cheating, as is any practice in which a double-standard is created - example: if making an on the fly change so that an encounter becomes possible is subjectively good, but making an on the fly change so that an encounter becomes impossible is subjectively bad - that is not holding to the same standard, which is unfair by definition.
When you're completely in charge of what the players are up against
This may be the major separation point in our views - I am not completely in charge of what the players are up against - they are.
I am in charge of what is present in the world, they choose how and if they will engage things.
if the adventure is too easy, that's no fun either.
Fighting a challenging enemy is fun. Fighting an enemy that you manage to completely stomp into submission is fun. Getting the snot beat out of your character is fun.
So long as any one of those is not occurring too often - at least that is the view my players and I share.
That said, I like the rolling in the open thing -- but it means if an adjustment is needed, it'll have to come from hp, attack bonuses or elsewhere.
I'd rather have my character beaten to death because I insisted on trying to fight an impossible to defeat foe than to know that I survived on the merit of a Judge saying "actually, the monster didn't have a high enough attack bonus to hit that time." or any other alteration of the rules.
The only time I have every out-right argued with the guy running the game was on the matter of his attempt, after setting an encounter upon the party that was far too potent for us to survive if engaged directly, to declare that my dead D&D character could be saved if someone healed him back to positive hit points before his next turn - which I refused on principle.
The die rolls in RPGs are not gambling (where it would be unfair to fudge); they are randomization
To me, that statement is synonymous to this one: "When is rolling the dice not
rolling the dice? When you are randomizing."
I know you are saying that a table-top RPG does not need its randomization held to the same standard as casino gambling does... but if I could afford to have dice of all types machined to the same tolerances as casino dice, then they would be all I would use at my table.
Strictly speaking, it's not the randomization that on occasion needs fudging -- it's the human input in front of the roll, fudged after said roll.
I have to admit that I don't even understand what you mean here... it's not the attack roll against an impossible to hit AC that needed fudged, it's the player declaring his attack in the first place that needed fudged?
If it is the human input that needs adjustment, why not handle that adjustment before or without rolling the die?