Chain lightning doesn't stack shocked

I'm running a mage focused on stacking every DoT that I can and it seems as though chain lightning will only stack shocked once. I believe that perhaps the same flag that prevents shocked from stacking multiple times from weapon triggers is accidentally being applied to chain lightning as well. What I've been able to confirm so far through testing:

Casting chain lightning on an opponent a second time BEFORE the shocked expires neither adds a stack of shocked, nor refreshes the duration of the existing instance of shocked.

Casting chain lightning on an enemy after it has had shocked applied from the Tempest ability or Balara's Fade Bolts ability also does not add a stack of shocked.

The Tempest ability and Fade Bolts WILL propperly inflict additional stacks of shocked on each hit on enemies that are already afflicted with shocked.