This is a lie. They didn't refuse. They didn't have it codified because they were trying to figure out how to define that. For example, one of the challenges IRS was having was someone reporting $390,000 but they actually earned $450,000. How do you deteremine that without an audit? Do you need a waiver? How does that get resolved without breaking the promise.
> Look at what they do, not what they say.
They were actively working on how to respect the promise in a reasonable way.
The IRS didn't follow the intended policy, getting bogged down in the details of how they would define that threshold (primarily, would somebody who understated their income to get below the threshold count as "under 400k and audited").
Not really sure why the OP is so upset - either way, the payback on additional funding to the IRS is almost universally stated as revenue-positive.