Hitbox directional indicator isn't visible with large mobs

When hitboxes are shown (F3+B), mobs with large sizes - e.g. scale 5 - have the blue direction indicator at the lowest scale - that is, it doesn't adapt to the larger size of the mob.

 

How to reproduce:
Summon a large mob - I summoned a Size 9 Slime.

Results:
The directional indicator isn't visible - it's inside the slime.

 

This also works with any mob, if their generic.scale attribute is increased.