Earlier quoted context omitted.
The first step to processing mail ballots is checking that the signature matches the voter's known signature (usually submitted at the time of voter registration). Are you proposing a conspiracy where crooks are somehow forging hundreds (if not thousands) of signatures? And there's no paper trail of communications or money changing hands to coordinate it all?
Signatures are, frankly, a bad way to determine if a ballot is valid or not. People's signatures change all the time and there's not exactly a science in determining whether or not two are the same. It's ultimately up to the counter to make that determination. Otherwise, I agree with your point. The reason ballot harvesting is much less of an issue than made out is because there's a vast paper trail with each mail in…
I don't believe 'signatures change' is reasonable or valid. By the time someone reaches adulthood and has an ID, their mark is likely to be quite distinct. Check your grandmother's signature sometime. My point being, that dismissal is not evidence or fact based, but likely aligns with your opinion.
>ultimately up to the counter
There's absolutely no reason to do that. Digital files already exist of all signatures and the envelope is coded to each voter. The comparison can be done trivially by image processing.