Creepers can destroy vehicles even if mobGriefing is set to false

This issue occurs with or without the "Minecart Improvements" experimental setting.

Steps to reproduce:

1. Run /gamerule mobGriefing false

2. Spawn a creeper and place down a boat/minecart next to it

3. Ignite the creeper using flint & steel or by aggroing it

Observed result:
The explosion from the creeper destroys the boat/minecart.

Expected result:
The explosion from the creeper does not destroy the boat/minecart.