Hitbox of mini player model isn't centred

The hitbox - shown using F3 + B - of the mini player model found in the inventory isn't centred the way it is for the actual player.

Ways to reproduce:

1. Press F3 + B to enable hitboxes

2. Open the inventory

Expected result: the hitbox of the mini player model is centred nicely, just like the normal player model.

Actual result: everything is slightly aligned to the right edge of the hitbox, instead of being in the middle. This results in the left arm being completely outside and the rest of the body "hugging" the edge of the hitbox, as opposed to being in the middle.