(minecraft:born_screamer) spawn event not working

I found a new spawn event called "minecraft:born_screamer" and have assumed that it's meant to be used to summon in Screaming Goats. If this is the case, then it does not appear to be working. I used the command "/summon goat ~~~ minecraft:born_screamer", but goat it spawned in seems like the default variant. I've stayed near it for around 10 minuets just to be sure.