Earlier quoted context omitted.
That case was against Medicare contractors. Not Medicare.
Jimmo v. Sebelius The named defendant was the Secretary of Health and Human Services. The suit was over practices followed by Medicare contractors, but it's not like they were operating outside the knowledge of Medicare, they were acting as Medicare had directed them to act. The settlement agreement has Medicare changing the procedures the contractors will follow.
"...in which the plaintiffs alleged that Medicare contractors were inappropriately applying an “Improvement Standard” in making claims determinations for Medicare coverage involving skilled care..."