The synchlink uses a compound cable, like the brake cable on a bicycle (there's an inner cable and a rigid outer metal housing).
The only motion that matters is the inner cable relative to the outer housing. The two ends of the housing can move relative to each other and it doesn't affect how much motion is transferred by the cable.
Despite the photo above, the cable between the two sides doesn't need to be in a perfectly straight line. Kinda like a Bowden tube works.