I'm not exactly sure what type of evidence you are looking for with respect to the assertion that auditing a paper ballot system is easier than auditing a electronic voting system. Auditing a paper ballot system is trivial: any person who can see and can count can do it. On the other hand, if you are relying on a software system you need to audit the hardware, the software, etc, etc which requires a lot of skill and is tricky.
"But how secure and accurate was the 2018 vote? It’s impossible to tell because the state and the company aren’t sharing the basic information experts say is necessary to properly evaluate whether the blockchain voting pilot was actually a resounding success"
Not impossible to tell. If you do a 100% poll of a given county and ask for statistics afterwards, you have an impromptu security analysis.
How would you conduct a similar audit of how secure a paper ballot is for any given system? If all you do is an audit of a single vote, then you're no different.
Until paper ballots can no longer be dumped in the trash, paper auditing is hard at best.