Only a few amount of illusioners hold their bows more diagonally

The bug

Only a few amount of illusioners hold their bows more diagonally. https://minecraft.gamepedia.com/Illusioner

How to reproduce

1. Summon a lot of illusioners.
2. Summon a NoAI villager.
3. If lucky, one of the illusioners will hold their bows diagonally while others hold it like skeletons.