The Bug

Passenger riding on a mob has a delay before it falls when the mob is killed. This can be easily seen with Baby Striders on top of adults.

Steps to Reproduce

• Summon a baby strider riding an adult strider.

  /summon minecraft:strider ~ ~ ~ {Passengers:[{id:"minecraft:strider",Age:-25000}]}
  

• Kill the adult strider and watch the baby strider closely as you do this.
• Take note as to whether or not baby striders riding adults striders have a delay before they're dismounted after the adult is killed.

Observed Behavior

Passengers riding mobs have a delay before they're dismounted after the mob is killed.

Expected Behavior

Passengers riding mobs would be instantly dismounted after the mob is killed.

Code Analysis

Code analysis by Avoma can be found in this comment.