After EXHAUSTIVELY examining them with a continuity tester, I discovered this:

Both the old and new cables symmetrical and are wired "straight through".  BUT, the new ones with the thumb screw have something very unique.  There appears to be a Normally Open  momentary switch build into the thumb screw, so that when the screw is not tightened down, it leaves one wire disconnected.

            Tab/Screw

0 2 4 6 8 10 12 14 16 18

1 3 5 7 9 11 13 15 17 19

Holding the cable to look into the pins, using the above numbering, it is pin 11, which has these particular switches inline.  And it may have a diode or resister inline under some heat shrink as well. 

It looks to me like an ATX 'start signal', and probably, it's intended to make sure the two devices ground planes are electrically bonded before supplying DC power.

I suspect it is superfluous and can be wired out of the circuit to perform asthe old cable, but I would not have any mechanical means of retention.

Am I missing anything?