Power Siphon double charge

A while ago I noticed my Power Siphon granting two power charges from single monsters from time to time. I eliminated the possibility that the charges would come from other monsters outside of the screen by isolating a monster against an area edge. I am also not wearing any gear with power charge functionalities and none of the passive skills mention this.

I searched the forum and stumbled upon an old post from last year saying that killing a shocked enemy grants a power charge. After some more testing it seems this is still the case, at least with power siphon. (Another player said he hasn't noticed gaining any power charges on his lightning archer, so this functionality could be exclusive to power siphon.)

This could be an old remnant that wasn't taken out, but if killing a shocked enemy with power siphon is intended to grant you a bonus charge in addition to power siphon's regular function, the skill gem description should mention this.