Earlier quoted context omitted.
If it is hard to get wrong, is it still dumb? Being able to verify with your own eyes that the redacted parts are indeed redacted is a pretty strong benefit to that process. You'll need to train staff to properly black out stuff (no idea what they do, heavy cardboard cut-outs or cutting out the censored content and using a black background for the scan?), but once that process is in place, it works. With software you…
Incidentally, you just wrote a pretty good argument for (political) voting on paper instead of via machines.
An election doesn't need to be tamper-proof we just need to be able to detect tampering well enough to make tampering a loser's game.