rotorque,
You are correct about the KAflex coupling. It has been in use since 1878. Ten years ago they were referring to it as 'Extended Service Life'
The subject of what constitutes a 'Constant Velocity Joint' is an interesting one. IMHO, it appears that all CVJs have one or more components that experience acceleration/deceleration. This component(s) may slide or roll and need lubrication, or it may flex and have a life limit.
Perhaps the claim to being a CVJ has to do with how large the oscillating component(s) is. Even a pair of universal joints provide a constant velocity, if these two universal joints are installed in phase with each other and always operated with equal angles.
Dave