This is an extremely weak straw-man argument. It doesn’t need to be on the blockchain, mobile, or even the internet. You can print out the cryptographic proof on paper if it pleases you.
How do you convince them the mobile app is doing what it says? There are so many layers of things that are completely invisible to a human without using other computer tools. Paper physically moving is way easier to understand and watch.
I observed the "audit" of my county's VVPAT. When the printout was found to be illegible, the admins just printed another copy. Proving, at best, the printer occassionally worked.
My county trashed our touchscreen voting machines.
Sadly, vendors, technophiles, and a certain type academic, remain undaunted in their enthusiasm for unverifiable elections.
Eg Adjudication of postal ballots, at scale, isn't any better than the touchscreens they replaced in that regard. How hard could it be? Well, the stack my county uses, for "efficiency", fully digitizes the audit trail.
