Tridents have the SoundEvent tag, but don't use it

The

SoundEvent

NBT was added to the arrow base class, and it used for arrows when they hit blocks or mobs; since tridents extend the arrow base class, they also have this tag, but don't appear to use it.

Additionally, the default value on tridents for this tag is also

minecraft:entity.arrow.hit

instead of the corresponding trident sound event.