From what I understand, every operator can select the point at which an FDM monitored parameter triggers an alert. This will inevitably mean that in different airlines, the very same event will trigger an alert in one FDM system, but not in another.
A typical system generates so much data, that it simply isn't possible to use it as the "spy in the cab" that some pilots seem convinced that it is. I've spent a bit of time with the Safety Managers in the airlines where I've worked so far, and the trigger points for the kind of FDM event where the Safety Manager registers any interest at all are well beyond normal SOP parameters, except where there is a hard limit, such as placard speeds.
The systems give quite a bit of wiggle room for the average pilot on a normal duty to do his thing without raising any eyebrows in the office. Very often, an event which a pilot feels must have triggered an FDM event, goes completely undetected, and only on receipt of a pilot report does the data get reviewed, and very often with no real concern from a safety standpoint.