The issues I have seen with active basses are down to the polarity of the wiring.
For the general active bass to power on when plugged in, the preamp takes power from the battery and the ground on the bass. The negative of the battery only goes to the jack socket. If you are using a stereo (TRS) socket, and you plug in a mono plug, as you would generally do, it shorts the ring and the shield together, as the mono plug doesn't have a ring. Therefore, if you connect the ground of the bass to the sheild, and the ring to the battery negative, then plugging in switches on. However, some basses put the negative to the shield and the ground to the ring, because in 99% of cases, it really doesn't matter, the short is both ways.
In the case of the WL20, it actually has a TRS plug, which it uses for power, so to enable the bass to switch on it has to route the negative of the battery on the tip to the shield, which it obviously does as it works. I heard cases that at least originally, it didn't work with basses that were the other way round.