You do not have any idea whatsoever how those systems are built, do you? Everything is logged, and logs changes are logged and logs change logs are logged and all those logs are signed and when the logger looses connection to loggable, then this is logged too and that is logged too.
And finally. The interest of knowing of who voted who is virtually zero. I admit that the principle of anonynous voting is good and needs to be guarded, but the real harm of leak is virtually zero too. The most bigger threat is manipulation of results.
You have no idea whatsoever how these systems are built.
You don't know because you haven't seen the software (or hardware) for them. You haven't because (I assume this part) you weren't one of the state inspectors, and what many (most?) of the manufacturers have done is to insist that no one ELSE be allowed to view the details since it's a "trade secret".
So maybe there is excellent logging like you describe. And maybe there isn't. We DO know that there have been occasional incidents of invalid vote reporting by the machines (such as [1] or [2]) that were not caught by such log systems.
You cast your vote at a github-hosted source code repository?
As René Magritte might have put it, "Ce n'est pas le logiciel". You haven't seen the software - you've only seen source code that may resemble what is running when you cast your vote.
And I don't really care what logs are kept, because any such log is one dodgy programmer, one bribed sysadmin, one lost private key away from being totally or partially compromised.
The system we have works and would require the complete and flawless cooperation of thousands of conspirators -- including mutually hostile, cross-checking party officials -- to subvert the outcomes.
