You are right Jim the AD 2012-0115E that was in effect at the time would have excluded G-CHCN.
However what data or analysis was done to to allow the formation of that directive?
If there is a sound body of engineering work then that would be fair enough but if it exists then it isn't in the public domain. Even if it was discussed between the operators it seems extremely odd that 2 (of 3 or the majority) have decided to monitor more closely than the AD. Which suggests the formation of 2012-115E is flakey.
If the logic was flawed then how and what is or should be taken as correct for the future?