Thats because like many other speed parts they are desighned for a chevy and modded for a use on a mopar. A mopar does not mount the axle in the middle of a spring like a chevy or ford but those springs are engineered for generic cars and they just move the axle mounting point and sell it for mopars.
I have not used nor looked closely at a fiberglass spring to verify this. If that is how they are made, then the thickness of the spring and its location could be a factor in the need for any traction enhancing device. However, if the frotn segment is trimmed shorter to fit a mopar appplication, that should still provide a thicker cross section than a competitors design which is a strength of the mopar design.
A fiberglass spring by nature is more rigid than a steel spring and in a road or autocross setting should not require additional traction devices, IMO, but no first hand experience here. On the other hand, a drag launch may need a device because of the signficant shock loading of the springs and the brittle nature of fiberglass.
