The Bug

Advancement criterions player_hurt_entity and player_killed_entity, death messages, and statistics such as minecraft.killed:minecraft.creeper don't consider damage and kills by igniting creepers to be caused by the player.

How to reproduce

To reproduce, you can try getting the Monster Hunter advancement by igniting a creeper (it won't trigger), killing yourself with a creeper you ignited (it won't say "Player was blown up by player"), and by checking your statistics page when you ignite a creeper to see if it increases (it won't).