The Bug
The Marker Entity can trigger the sculk sensor if it is /killed. Other technical entities can do the same, even though when they "die" without /kill, it does not trigger the sculk sesnor. For example, when lingering potions & dragon breath clouds dissipate naturally, there is no sculk signal, but when a cloud is killed with /kill, it does send a signal.
Here are all the entities that trigger the sculk when they are /killed when they shouldn't:
Area Effect Clouds
Armor Stands**
Arrows
Boats**
Display Entities: text_display, item_display, block_display
Evoker Fangs
Experience Orbs
Falling Block
Fireball entities
Firework Rockets**
Interaction entity
Items
Item Frames & Glow Item Frames
Leash Knot
Llama Spit probably
Marker entities
Minecart entities**
Primed TNTs
Shulker Bullets**
Thrown Entities: Egg, Ender pearl, Experience Bottle & Snowball
** (It's hard to tell because they tend to trigger the sculk sensor in other ways)
The rule should be that if an entity's death can trigger the sculk sensor without /kill, then it can trigger the sculk with /kill, but if the only way they can "die" is with /kill, then it should not trigger.
Can confirm.