2) Assuming it's even true, what should this person do instead?
3) What do you think the outcome would be if this person did contact Microsoft? Since it's a mistake, I assume something bad?
Since this is copyright infringement, the copyright holder could file a DMCA takedown notice.
https://github.com/microsoft/cups/commit/ad69bcc78bdea3fea3f...
Edit: To give a bit more nuance, I would guess that the actual bot changing the LICENSE files is not a mistake, but working as intended. What could, however, be a mistake is thinking that licenses can be legally overwritten. It wouldn't be a "rogue engineer" kind of mistake. Certainly several people at Microsoft have signed off on this.
That's not a bot.
https://github.com/microsoft/cups/commit/8100595a3a3a6d5c7d0...