Gamerule doMobLoot doesn't affect xp drops

The gamerule doMobLoot when set to false still allows mobs to drop their xp. I am working on a map where I want to use the xp level as an indicator. When the player then gets more xp, the level is incorrect and leads to wrong behavior.

Steps to reproduce:
1. set gamerule doMobLoot to false
2. Kill a mob or animal
3. See that it drops xp