Steps to Reproduce:
1) Run 

/summon spectral_arrow ~ ~5 ~

2) Then, jump into lava and see the death message

Expected Result:
"Player tried to swim in lava to escape Spectral Arrow"

Observed Result:
"Player tried to swim in lava"
 

Entity Type	Direct death message	"was doomed to fall by _" (take damage from entity, then take fatal fall damage)	"was blown up by _" (collide entity with End Crystal and take explosion damage)	Any other death message
Area Affect Cloud	- "was killed by Area Affect Cloud using magic"
Arrow	- "shot by Arrow"
Potion	- "killed by Potion using magic"
Spectral Arrow	- "shot by Spectral Arrow"
Shulker Bullet	- "slain by Shulker Bullet"
Small Fireball	- "burnt to death"
Fireball	- "burnt to death
Trident	- "impaled by Trident"
Falling Block	"was squashed by a falling anvil"   "was skewered by a falling stalactite"