Prematurely ending Heat Wave breaks Fireball DoT

[notawaifu]

Context: "Deals x to y Fire damage. Counts as a Primary Bolt. When both Heat wave and Fusillade are on cooldown and not in effect, Fireball deals an additional 75% of its damage over 5 seconds. This effect doesn't stack." - Fireball
Expected: Fireball leaving a DoT as per its skill description "When both Heat Wave and Fusillade are on cooldown and not in effect, Fireball deals an additional 75% of its damage over 5 seconds."
Observation: No DoT is placed on the target.
Repro Steps:
- cast Fusillade
- cast Heat Wave
- cancel the Heat Wave buff
- cast Fireball
- no DoT


thanks qUiXui