Part of the problems with servo transparency is the bilateral airworthiness agreements under which the helicopter was originally permitted to enter the country.
The helicopter was certified originally in France, and because of a bilateral agreement between France and US, if it is certified in France, then it is accepted with minimal fuss in the US for Part 27 helicopters. For part 29 machines, the process is a bit more rigorous but not much different.
The French seemed to have few problems with the servo transparency in certification, and the US was relatively powerless to not accept it (or they may not have seen this during the FAA familiarization flights).
Things like this that are discovered later in life become more a political issue than a technical issue - and political issues are nearly impossible to solve any time.
As an example of this - there is no such thing as night VFR in Europe for single engine aircraft. So the EC-120 didn't have much beyond a single wander light to light the instrument panel when it was first certified. That was caught in the approval for use in North America (both FAA and Transport Canada caught the problem) and the EC-120 had to have the instrument panel lighting changed significantly for N. American sales.