Those came on later model ZX's, if I remember correctly. I've used them before on my trans.
They have two tiny springs inside, to dampin the feel (I guess that was the reason) which allows the handle to slightly move up and down.
I know the 83 5 spd I had, came with taller ears for the shifter pin to fit thru, and it's possible the pin height may have been slightly raised to allow for this shifter handle, since it is oblonged, and taller (in my opinion).
I hope I didn't add to the confusion with my post, but this is how I remember my experience dealing with that shifter handle...