It's unfortunate that you didn't stop for a second to reflect on your response here, considering for example what pdx1M laid out, rather that essentially stick people with a cheater tag.

We ain't talking murder statutes here, and simplistic rules for things like airline flights (which are really incentive rules) can often achieve the opposite of the intended effect.

Dialogue and understanding of the adverse effects of one's rules, schemes, etc etc can and should lead to rules that are better all around, arguably not just when it comes to airline incentive schemes

In this case, you have a flat out mistake on the part of the airline - which happens to favor its customers. They could have let it go. They could have looked at it after "closing time" and fixed it where it was wrong - consider that if they have to credit the correct bonuses, they will need to work out the logic for what is and is not correct to re-add the correct miles afterwards anyway, which will be the exact same amount of work on UA's part. They could have sent a message now stating how they realize they made a mistake, and would be working to rectify it after the promo date closed, simple as that.

But no, they chose an approach that will be more work intensive (as they remove everything first, then need to work out the right-from-wrong logic to add the right amount of mileage) and guaranteed to inflame folks needlessly. I really cannot for the life of me understand how anyone could reach the conclusion that this approach was the preferable one. Amazing, simply amazing.

EDIT: and yes, accounting shenanigans had crossed my mind, quarter end accounting seeing something off, triggering reactions, etc etc. It's probably the only way to come up with some sort of reason why pulling miles now across the board might make any sense - PR disaster notwithstanding.