Not sure if this is a bug or by design. But I notice in the latest snapshot an awful lot of this...
[16:51:55] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:51:56] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:51:58] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:00] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:06] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:08] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:09] [Server thread/INFO]: [STDOUT]: minecraft:player_killed_entity
[16:52:09] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:31] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:31] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:31] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:32] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:33] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:37] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:43] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:45] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:45] [Server thread/INFO]: [STDOUT]: minecraft:player_killed_entity
[16:52:45] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:48] [Server thread/INFO]: [STDOUT]: minecraft:entity_hurt_player
[16:52:48] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:49] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:50] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:51] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:51] [Server thread/INFO]: [STDOUT]: minecraft:player_killed_entity
[16:52:51] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:51] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:52] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
[16:52:52] [Server thread/INFO]: [STDOUT]: minecraft:player_killed_entity
[16:52:52] [Server thread/INFO]: [STDOUT]: minecraft:player_hurt_entity
If this output could be made to include the source player name and the entity type targeted... I could use that information to compile some good stats by listening to the console (which I already do) without having to use the scoreboard or parse/retrieve the json