Slightly late to the thread, and acutely aware of possibly relevant Ninjaing (or contrapuntal Samuraiing) after the message I read that sparked this reply, but...
Insofar as Doom's godmode, useful for wandering around a level in a leisurely manner, I found, getting an insight as to the layout, looking for hidden bits[1], but saying "Yeah, I completed Doom while invulnerable" was not a bragging point. Even "Yeah, I completed a Doom level in half the par time, while invulnerable" isn't a bragging point. Especially if you've cheated yourself a full set of keys, from the start.
Savescumming is something I have a lot of potential to do, for I habitually set up the full seasonal saves. But usually the only thing I might use it for is to go back and re-embark, exactly as I originally embarked (without having to re-find the exact spot) in order to build the entire fortress
again, but this time
one tile to the left!!!. The second reason I might go back to seasonal saves (or an actual user-generated save) is when I'm trying something out (a novel layout of drawbridges and levers and things, maybe), and I deliberately note that "What happens from now on in is going to be erased from history, and things redone as if they had never happened". Very rarely will I even
consider bringing a save back, just because I missed a caravan departure time or somesuch. (I'm fairly good at making sure those events don't occur, of course, so maybe it's just not the imperative it might once have been).
In almost all cases, the savescumming is (by accident or design) accompanied by having to micromanage a godawful lot of stuff all over again. Never[2] have I used it to spam exploratory tunnels and then re-do from the start knowing
exactly where to head, without all the other (wasted, useless or even downright dangerous) effort being spent. But, in the same way that making a trial run of a Doom level with [God-mode, no-clipping or whatever] then leads to multiple serious attempts in full on hardcore mode, I would consider it perhaps a shortcut to gaining experience, but in no way ruins the "true run". (Which, in DF, may be the first fortress embark where it is all honestly single-timeline, or deviations at least are in good faith... But that depends on your personal values as well.)
My current fort has enough self-imposed restrictions (single rock-type block walls, etc) that I could probably even justify losing some of the other difficulty, given the addition of my own task-list that I need to obey. That may well be more relevant. The game is what you make of it.
[1] Using the map-revealing cheat was far more cheaty, given you could then home in on hidden bits far easier, or at least knew there was a bit that leverontheothersideofthecomplex might open. But the best ones were essentially time-coded, so you still needed to hop and skip across the top of a complex layout of tall pillars to get there before it closed, so maybe it was just poor level design that allowed such easy pickings...
[2] Ok, so not recently. I know I did it once or twice, a long time ago, and even then I was considering it more 'learning' than 'beating the program'.