<< however a CAMO has to be certain of the facts, and most are not prepared to risk overlooking someone else's mistake >>
What mistake? In the case of French registered aircraft, the NAA made the rules, approved the maintenance programme, issued the ADs, approved the mods, and carried out all airworthiness reviews on the aircraft since it was constructed.
For a UK CAMO to suggest that a back to birth inspection is needed in case 'someone made a mistake' is just pure extortion.
Same deal for G reg aircraft, where the CAA did the inspections before issuing a new C of A. No it seems to me that some engineers are using the new part M as a money making enterprise.