No statistics for amount of killed withers or enderdragons in statistics tab

There is no section for the amount of withers killed or enderdragons killed.
For example;

Blaze
You killed 176 Blaze
You have never been killed by Blaze

There should be;

Wither
You killed 13 Wither
You have never been killed by Wither
,
Ender Dragon
You killed 11 Ender Dragon
You have never been killed by Ender Dragon