Earlier quoted context omitted.
The problem, as I understand it, is that if you can prove to yourself that your vote was counted right, you can also prove it to the guy with the sledgehammer next to you saying "it would be a shame if something happened to your family, so prove how you voted"...
By that logic we have to get rid of mail-in voting as well because there could always be a sledgehammer guy standing next to someone in their own home.
And the biggest problem of this all is that it's basically impossible to prove because there's no meaningful identifier at any given point in the process. The only real evidence you'd have is a bad signature, yet in 2020 some states ceased comparing signatures and signature comparison was, in general, bizarrely under attack by certain interest groups.