Some Bluesky asshat politics super-nerd posted it without a source. I googled and I couldn't find it. I did find this though...
[Whistleblower letter to Sen. Richard Blumenthal (D-Conn.)] “When ballots are submitted to USPS in large-volume batches, if any one ballot in the batch cannot be verified against the Portal, all ballots in that batch will be rejected.”
In other words, if there is just one ballot with an issue — like a name that doesn’t match up identically to the name states previously provided to USPS — out of a batch of 10,000, then USPS would refuse to mail all 10,000 of the ballots, not just the flagged one.
AernaLingus's comment has a link to the source.
For clarity - a Bluesky comment
Just to be 100% clear here I just read the source materials and the whistle blower is describing the process for handling ballots that the state is mailing TO voters.
Has anyone actually gamed out what getting rid of vote-by-mail would actually do to elections?
Like, aren't rural Republicans and immobile boomers more likely to vote by mail anyway?
Dems and urban people are a bit more likely to vote by mail
This is the kind of data that would be a lot more useful if it were separated by geographic area. In some states you can vote by mail if you request it in advance and you have to provide a reason. In other states, it is the default and you automatically get mailed a ballot by your county. Obviously in states where it is the default option it is far more common to vote by mail than in other states. So there is definitely skewing of the information that comes from that alone when lumping all of it together