Cast while channeling impending doom with two curses

Using Cast While Channeling with cyclone;
Two curse setup in body armour, links in order : Despair - Frostbite - CWC - Impending Doom - Cyclone;
Along with impending doom;

Not sure if my testing was properly conducted but using the mouse cursor to manually target away from the character, while channeling, and cycle the curses on enemies doesn't seem to proc the impending doom explosion. Using Cast on Critical with two curses/Cospri's with one curse and another Cast on critical setup with one curse or manually cycling between two curses with impending doom all trigger the impending doom explosion.

Another thing, might relate to the issue (if there is one) with CWC, if I channel enough so that one curse is cast on enemies, then remove the CWC gem and manually cast the second curse, the explosion once again does not go off. Also while using CWC with the cursor away from the character does not trigger explosions on cycling, If the character enters a pack of enemies while channeling, the explosions start going off.

All the testing was done with default curse limit of 1.

Not a bug.

Read Impending doom's tooltip again, carefully.

Cannot be triggered. CWC is a trigger.