Apple Insider reports this incorrectly, a Recovery Key is independent of Advanced Data Protection.
Additional context on this case and similar cases: https://archive.is/1NMCR
If a user or thief has turned on a feature called Advanced Data Protection, all of that data is fully locked down and not even Apple can access it. But in cases where that advanced encryption isn’t being used — like Mathews’s — Apple isn’t hamstrung by technical limitations; it’s choosing not to return people’s data, experts allege.
Apple has “never expressed to us that they are unable to give the information back,” Breyer said.
Apple Insider is merely assuming — probably incorrectly — that ADP is being used.