I have a set of 72 seat tracks and there is no spring or wire connecting the two tracks together. I have looked in all the catalogs I have but no one seems to address this piece. Someone had rigged up a piece of electrical wire but there must be something better from the factory.
The intent of this (spring or wire) is to release the inboard track latch when the person used the outboard release handle to be able to slide the seat forward or backward..
Just make one out of mechanics wire or music wire. Like you say, all it does is release the other latch, long as it releases and latches again, it's all good. Could always grab one out of some kind of bench seat at the bone yard, and cut it down.
As far as I know some of the interior tracks are just free floating and others need a connector of some kind to release a latch on the interior track. I had set of buckets that I think had the original release mechanism and it was just a piece of wire similar to a coat hangar just a little stiffer. Even at that they were a little sloppy so I just twisted up a new wire out of maybe four pieces of safety wire and it has worked flawlessly for years.
On a bench seat,the wire runs from the driver's side thu a metal loop in the middle of the seat (connected to the seat) and to the rear of the seat, then to the passenger side runner. The loop on the seat is connected to the solid metal part of the seat. See the attached picture.