So are you suggesting that it's okay to adjust a monster's HP during the fight (up or down) to set up a result, but changing a die roll is not? That doesn't make much sense to me. Because all that means is that you could theoretically decide to adjust a monster's HP up high enough to just counteract the hit and damage roll you weren't willing to change so the monster ends up in the exact same place-- just as if you had fudged the attack roll to a miss. Personally... I don't see one being any better or worse than another.
And this is really why I think fudging is "good"-- because a large number of people here are giving all kinds of scenarios where changing game mechanics to alter results is fine for them in maybe
one specific way and which they don't consider it "fudging", but yet will believe that doing it in all different other ways is bad, bad, bad. And it seems like every single one of those people have a different thing that they say is okay.
To me though... when anyone has to go over their own particular details and picadillos with such a fine-toothed comb to justify their preferences... I just throw my hands up and say "Why get so hung up on it?" Why waste your own time with those attempts at justification? Just be comfortable with what you are doing and not care how anyone else thinks about it. Just be comfortable with fudging as a "thing" you and/or other people do. And not worry about it!
People fudge. It's fine. You fudge. That's also fine. Other people fudge only when they tell their players openly that they are doing it. Fine as well. Other folks say they don't fudge at all but sometimes just give free successes when the players did something cool. Fine again. And some people run their games as though they are just like a computer program and make no allowances or changes or fudges or anything. Fine.
Do whatever you want! Just don't put yourself out over it. You have better things to do than trying to fool yourself.