Invoker Hand of Chayula Mark questions

Hail.

I've been looking up builds on poe.ninja to see what the top people are running for Flicker Invoker and noticed that most of them are using Hand of Chayula with this setup:

- Freezing Mark, Voltaic Mark, Sniper's Mark
- Rapid Attacks III
- Eternal Mark

However, as far as I know, mobs cannot have more than 1 Mark active at a time (Deadeye had something akin to Whispers of Doom and it got nerfed?).
I've done some testing and only ever seemed to get the Cold Damage buff from Freezing Mark (UI + gameplay effects enforce this) despite shocking the mobs.

So what gives? Am I misunderstanding the Mark mechanic or is there some secret tech/exploit I'm unaware of?

Examples:
- https://poe.ninja/poe2/builds/vaal/character/CliffXL-2955/Spiritofbalance
- https://poe.ninja/poe2/builds/vaal/character/Mercedes-6076/MercedesxBB
- https://poe.ninja/poe2/builds/vaal/character/Ryux08-0335/RyuxX_
- https://poe.ninja/poe2/builds/vaal/character/Shakrala-0654/ShanJe