Anyone else notice a trend here?  All the models that benifited from some differential have a few common charactaristics.  A flat bottom or otherwise cambered airfoil and often are high wing designs.  The 4-40 is an exception on the high wing issue but it has the cambered "lifting" airfoil".  It also had a longer aspect ratio wings than most aerobatic models.  It's also a model that tends to be flown a little slower on most occasions.  All those issues add up to contribute to a more noticable adverse yaw issue that is helped by adding some differential.

Another little factor.  Adverse yaw shows up more when the model is flown at higher lift coefficients.  Sort of like high wing trainers by students that are learning.  And it'll also show up when you ask the down aileron wing to suddenly do a lot of work.  Like with extra throw and full travel commands to perform a quick roll.

But the Laser and other such designs use a symetrical airfoil  So when both ailerons alter their angle plus and minus the airfoil is still symetrical from side to side and they both just altered their angles of attack by almost the same amount other than the angle of attack for the model to stay in the air.  So they pretty much generate the same drag for the same travel be it positive or negative.

Now near to the stall adverse yaw will still be an issue and some rudder added in will help.  But it's not a linear problem.  At lower lift coefficients, like when flying fast, you won't need any mixed in rudder because the adverse yaw will be so minimal as to not be noticable.  So the effect will be to hurt the maneuver at that time.