John: I'm getting my part numbers mixed up here.
The original version of the AD required periodic inspection, and replacement if cracks were found.
Mr Kenyon's case is that it should have specified replacement with the redesigned "thick-wall" cluster, rather than allowing another thin-wall cluster to be installed.
Schweizer specified replacement with a thick-wall cluster, but the FAA (and the CAA) did not.
It's clear that the inspection regime didn't cure the problem, as people kept on being killed regularly for decades thereafter, and are still dying.