So in the end, this is just one piss poor managed division abusing another piss poor managed division. Who gets the heat? Probably the lowest level people.
Why "wipe" them? That seems unnecessarily punative.
You can see the "don't give a shit I work with a predatory organization" oozing from everywhere.
The security guy is trying to claim that they've sent out many many notices, but really this is just an excuse to abuse other people in a machiavellian abusive organization.
"Service Desk is now aware that everyone else except them was aware, and now IT is absolutely incandescent." Whoops, missed an email and a meeting in there bucko.
And it's the SECOND company where this was "implemented" or "specced"? This sounds like someone checked a box or compliance or ass-covering upper management slid this under the table, but all the people it ACTUALLY AFFECTS didn't get any input or opinion on the matter. And when push came to shove over funding it that person had probably moved on to bigger and better things.
So since you get to do it, you seem to be gleefully doing it. Great job.