No, it doesn't. Sometimes it actually validates the choices made, provided they were good ones...
The two are exactly the same. In both cases you are, on the fly, adding or subtracting from the world that was previously created. This point is so obvious that I am beginning to think some of the anti-fudgers are being disingenuous.
Changing the past and changing the future are not the same thing at all, and you know it. One is immutable and the other isn't. One has already happened, and the other isn't set in stone. I want the plot to remain consistent. Rectonning is implicitly introducing inconsistencies and leads to contradictions. Sometimes this is unavoidable, such as telling the group, ok guys, we're gonna go ahead and forget that happened because I made a mistake in the rules and suddenly Bob isn't dead any more.
Slow down, and consider very carefully the language you're using here.
What? No. If someone is claiming cheating is ok, that's on them, not me. The language I use is a reflection of my understanding of the rationalizations I see for cheating in this thread. I will use the word cheating any time it's appropriate, like this one, because changing HP when there is no rules reason for it is cheating. HP go down when damage is taken, and go up when healing or rest is taken. And at no other time. Period. That's what the rules state. Feel free to ignore the rules, but then don't claim outrage when others call you out on it.
Life isn't fair, true. Now I can't speak for everyone, but the last time I checked D&D was a game.
Yes, and while playing games players can and often do, cheat.
Saying it's okay to change the number of monsters, but not the number of HP they have makes no sense to me. If you want to play that way fine. If you want to play that once it's down on paper it can't be altered, fine. If you want to play the game without dice and just talk through everything that's fine too. All the shades between the latter two examples I just gave are fine too. But telling people that fudging is dishonest, cheating, against the rules, or what-have-you is problematic, at best.
Problematic for you maybe.
Let me explain the difference to you once again. As a DM, I control the world and the monsters, their motivations, their activities, their location, their number. Right? Right.
An existing monster's current HP total is max unless it was injured recently, usually by PCs. Right? Yes. If you increase their HP artificially without giving them a rest, you are effectively giving them additional healing potions or undoing the effects of some portion of attacks the players have dealt it. That's retconning and therefore cheating. The ways that HP change, up or down, are strictly defined by the rules and not by some arbitrary DM ruling like "I rolled 7 damage, but just take 5 instead.". That's not a game, that's a waste of time.
If a monster is at 2HP and about to die, and suddenly I give them 15 or 20 bonus HP, and after the fight the players add it all up and say, huh? Why did that orc have 2x the total hit points it should have? They would start asking questions. Trust is lost. Same thing if I as a DM record how many HP I've dealt to a player, and when I crit the player and know it's likely to bring them down, and it doesn't, and I recalculate their HP and find out they haven't the proper total, that I call cheating. Cheating in this case is symmetric. I can't tell PCs they have to record their HP faithfully if I don't hold myself to that same standard. Because I like being fair and playing by the rules.
Show me one place in the DMG that states it's ok to change the HP of a monster on the fly mid-combat, or somewhere else where it says it's unfair for additional monsters to start approaching the noisy commotion they hear down the dungeon corridor.
It's funny that you should even mention that I would enjoy playing a game of D&D without using dice, because I wouldn't. I like that the dice are impartial god-like determiners of outcomes. It's because I want the dice rolls to have meaning that I don't want the HP totals changed arbitrarily after the fact.
Fudging is synonymous with cheating. Just like fibbing is just a prettied up way of saying "lying". Using another word that means the same thing doesn't change the reality of the situation. Let's be real here. Pretending like fudging isn't cheating doesn't make it any less dishonest or acceptable. It's not dishonest for a DM to bring in more monsters to harangue the PCs in the middle of a battle, that's actually part of their expected duties and it is completely above board. It isn't fair, however, to erase damage they've already given or taken to make monsters last longer or die sooner. Longer combats aren't more interesting anyway. Plenty of BBEG villains have been one-shotted in popular entertainment. It's getting to them then rolling that natural 20 that's the satisfying part. Unless they win initiative and do that to your PC first.
Fair's fair. Keeping enemies around longer just to prolong the fight is not a good way to make the fight more interesting anyway. So why cheat? Don't do it. Play by the rules, and learn to adjust combat difficulty by increasing the number of monsters or hazards or giving the enemies a few healing potions instead. But for goodness sake, don't erase the damage your players just did to it so it will take them another round to kill it. That's not only cheating, it's lame.