So what.
And if you have a VM running, you can snapshot every move. And rewind to where ever you want, throwing away all random-mess, or not depending on the randomizer used.
If you have to copy your file on every step you done so far, its already a pain in the butt. If you store some global additional indicator data at some places in the game unrelated to the slot, and overwrite this thing like every 5 seconds even when idle (and of course when leaving the game) you need 4 files to save after every step. This reference might such simple thing like the number of all intermediate safes since the mission starts. Connect it with the random number generator outputs (its seed saved with the mission data and randomly chosen at game starts) you can't even do the exact same move repeatedly for getting different results, but have to do another thing (though you might want to do another thing anyway). What if that random generator choose where to write and read the reference out of 30 unrelated files (like mapdata, the executable etc.). Then you have to overwatch the file system very carefully... or have to mod your safe game mechanism...
There is something called convenience. The magician may design the safe system convenient for breaks and inconvenient for safes on regular basis - and that might be good enough. :-)
