AH are in a terrible position; If they genuinely believe that the accident was caused by other factors than the gearbox (and surely they must) then all they can really say is that there is no reason to stop flying it. They can't give vent to their full suspicions for a whole variety of reasons many of them to do with liability. If they don't have private evidence to support this (surely they must)they are heading for a Gerald Ratner moment.
Ref: this ^^
What couldn't they say and more to the point why wouldn't they say?