On further reflection, something else becomes clear regarding FS jump nodes (assuming they are traversable wormholes, which they appear to be). That jumping through a node gets you to a new system before light does is obvious, and thus there is a sort of relativistic time travel involved. However, jumping through a wormhole would not produce the differently-aged-twins phenomenon in and of itself.* The time lag situation would only arise if 1) the positions of the jump nodes moved in relation to each other, or 2) one of the mouths was situated in a much stronger gravitational field than the other.
If the two mouths (i.e. FS "nodes") of the conduit moved relative to one another, a time lag would occur between the two points proportional to that movement. However, this time lag would be no more significant than that between, say, Sol and Delta Serpentis now (and that isn't much, since they aren't moving all that quickly in relation to each other). It is worth noting that jumps to systems nearer or farther from galactic centre would exhibit more time lag, since systems nearer are rotating around the centre faster than those further away.
Since FS jumpnodes are naturally occuring and can't be towed around like those in the paper linked above, the only other important question is where the mouths of the wormhole are in relation to their stars. If there is a significant difference between the gravitational forces in operation at the points of space where the mouths open, a time lag will result in proportion to that difference. So if one node opens at a point near the outer edges of its host system, and the other close up to the star of its host system, a significant time lag will result.
Given the way jump nodes lie in FS (i.e. non-humanly moveable and never very close to the host suns), the time lag effects in the FS universe would never be very considerable. (Indeed the effects across a single system might be greater than between systems!)
*Since space is collapsed to a minimum in the wormhole, the distance traversed is short, requiring no near-lightspeed travel, and thus producing little more time lag than a trip to the corner store.