Not A Bug KOing with Rocky Helmet prevents Knock Off from activating

[MAMS_22]

What type of bug are you reporting? Mechanics

What is the bug?
In a gen 9 random battle, my regigigas (already inflicted with a burn) was facing a vaporeon. Vaporeon was switched with pecharunt and regigigas used knock off. Pecharunt was hit by knock off and was holding rocky helmet. Regigigas took damage from the rocky helmet and fainted but the rocky helmet wasn't knocked off.

https://replay.pokemonshowdown.com/gen9randombattle-2257125338

Turn 18

Are you able to replicate it? If so, how?
I don't know but here's the replay

https://replay.pokemonshowdown.com/gen9randombattle-2257125338

Turn 18

 

[A Cake Wearing A Hat]

If the Knock Off user faints from Rocky Helmet, the Rocky Helmet is not knocked off. This is an intended cartridge mechanic.

 

[MAMS_22]

If the Knock Off user faints from Rocky Helmet, the Rocky Helmet is not knocked off. This is an intended cartridge mechanic.

Thank you