Buy a 3D printer just to create a Seed Backup Jig? Hmm, I guess that would be overkill.
What if we assume that 3D printers log the data of what you have printed?They both do store the 3d model that you want to print (it's a feature), but you can format the SD card afterwards or just delete the file. I don't think they have any hidden 'logs' of models, but since they are open-source everyone can check for themselves.
Marlin also doesn't have any internet access, as far as I know (haven't used it in a while). So there is no uplink to anyone's servers whatsoever, i.e. no risk of anyone knowing what you are printing as long as you own your own 3d printer.
Bottom line though: you don't need any printed jigs. You can just do the washer backup by hand.
That only works if you don't buy too much unnecessary stuff, otherwise you'll turn into a hoarder. I'd say a box in a garage is a good place, usually those places store decades worth of items that "may come in handy some day", so it doesn't stand out.
