I believe so, yes.
One invalid/illegal mail-in ballot counted as “legal” spoils the entire universe of mail-in ballots.
State by state.
The key is the word “anonymous”.
Once counted among the “legal” ballots its anonymity makes it impossible to retrieve and verify.
You must throw out the whole batch.
For those who work in the kitchen, even the smallest portion of egg yolk in the separated egg whites ruins the whole merengue.
It's true. You can't make meringue with the presence of ANY fat.