Susier,
The issue with the G650/GIV you are referring to was the flight engineers incorrectly calculating the V2 speeds too high as well as making an incorrect assumption as to the stall AOA in ground effect. The net result of this was that the flight test crews were making aggressive rotations and steep climb outs in an attempt to not exceed the targeted V2 speeds and achieve the lowest possible balanced field length numbers for the aircraft. In the case of the 650 program this resulted in several wing drops during flight testing that were initially attributed to incorrect pilot technique, it took a tragic accident to "wake up" the engineers and get them to re-examine their calculations and uncover their erroneous assumptions regarding in ground effect stall AOA and V2 speeds. As Susier correctly points out the 650 accident had nothing to do with its flight control system, rather just incorrect performance calculations.
In the case of this GIV accident the fact that the aircraft appears to have come to rest (with considerable energy) some 2,000 ft beyond the departure end of a 7,011 ft runway makes me think this may not have been an aborted take-off over run. For a relatively short flight from Bedford to Atlantic city it is likely the aircraft only had a 10,000lb fuel load which would result in a BFL less than 4,000ft.