Dying while riding an entity only respawns the player next to that entity if the gamerule doImmediateRespawn is true

The bug

I am using the gamerule "doImmediateRespawn" on. When I /kill or something kills me while i'm sitting on something, I respawn as if i just stopped sitting.

To reproduce

1. Go far away from your current spawn point

2. Run /gamerule doImmediateRespawn true

3. Summon a pig

4. Saddle the pig

5. Start riding the pig

6. Run /kill
   → ❌ You spawn directly next to the pig