Hexproof + Hexproof bypass + Impending Doom weird interaction/bug

Observed behavior: Impending Doom (ID) fails to trigger its Doom Blast when cursing Hexproof enemies with a Curse that can affect Hexproof enemies.
Expected behavior: ID triggers its Doom Blast when a Hex is removed from an enemy, regardless of Hexproof modifiers.

Steps to reproduce:
1. Allocate Whispers of Doom and equip Vixen's Entrapment Unique Gloves, socketed with three Hex Gems.
2. Equip an ID gem (alternatively, Foulborn Doedre's Scorn or a relevant Forbidden Shako) linked with another Hex gem.
3. Allocate a Notable from a Small Cluster Jewel granting "X Hex can affect Hexproof enemies" for the Hex linked with ID e.g. Misery Everlasting for Despair.
4. Find a mob with the "Hexproof" modifier; individual modifiers and map mods both work.
5. Curse the Hexproof enemy with the ID-linked Hex and observe that Doom Blast fails to trigger instantly, as it should with the Vixen's Entrapment setup.
6. Unallocate the Notable Passive from step 3 or link your ID with a Hex which does not bypass Hexproof.
7. Curse the enemy again, and observe that Doom Blast triggers correctly.

Please note that it may be possible to reproduce this interaction without all the steps and conditions fulfilled (e.g. lower curse limit); I haven't tested this very thoroughly.