See summary. This bug probably occurs due to the trident's entity being derived from the arrow entity.
How to reproduce:
Summon 3 creepers in a row that have
NoAIsetPut down a repeating command block, set it to "Always Active", and put in the following command:
data merge entity @e[type=trident,limit=1] {PierceLevel:3}Throw the trident at the creepers, then replace
tridentwitharrowShoot the arrow at the creepers, they all get hurt
Then replace the command in the command block with the following command:
data merge entity @e[type=trident,limit=1] {ShotFromCrossbow:1}Throw the trident
Can confirm in 21w05b.