Above that, as leniant as Toady is to all the legitimate save-scumming that he allows to be done1, it may not be in his plan to make it as trivial as "quit without saving" atop of pause+save+quit and retire+save+quit, etc. And, from the player's side, balance the imminent cries of anguish as the wrong key-combos pressed leads to a player unwittingly not saving their pride and joy of many game-years (or one rathe complicated season...). Whilevan awkward-but-doable reversion technique, that goes beyond the trivial in the active rejection of the game's progression, fits much more with "story generator" pardigm that doesn't have inbuilt rewinds/do-over features either.
So consider the possibility that he doesn't want to replicate this DFHack function in vanilla2. He's happy enough that it's doable, but it's not in his vision for implementing in his interface. At the moment, at least. Given how it would be a mysterious option to omit or overlook...
That said, it never does do to process-kill things trivially, just in case of memory leaks (at the OS level, rather than the application, which can't be expected to clean up its spilled giblets after its own killed corpse is removed!). Still, should be safe enough at the disk-data level (so long as you aren't doing it during a seasonal backup save, which you might have to avoid loading in, incomplete) and a properly rebooted machine can reset ram-data sufficiently, if it comes to that.
1 There are ways to prevent, or at least count, rewinds of aborted games... If, as a games programmer, I was trying to put the 'dev' in 'devious', I could make it subtly ramp up the odds against success for every attempt to avoid bad luck. Karmic difficulty could even ensure that the rolling total of randomised combat rolls adjusted to keep the average as intended, so that redoing each and every failure in the pursuit of a success (by any simple measure) would lead to a near-certain failure beyond a certain point. Wouldn't be proof against back-up and restore of all the right files/etc, but that's why I'd make this a subtle effect using unadvertised vectors, with a second-tier system to spot 'trivial' get-around-it behaviour which perhaps renders all savegames liable to the karma... If I were inclined to do that kind of thing. Which I'm not, and neither (I presume) is Tarn. Just saying.
2 Actually, it'd not even be as technical as that. Tarn does not need to try to work out what complicated stuff DFHack does and redo it in his own core code, he can just amend his existing core save+quit code to allow a simple branch to skip over the existing saving part. In fact, I'd be surprised if this isn't a Dev-Flag-Only feature already in there, for testing purposes, like the ability to place already moving minecarts with customised contents and/or passenger in mid-air wherever the cursor is, when trying out the mechanics of such situations.