Inconsistent Z-fighting on composite 'item/generated' item models

When creating a composite item model definition using ‘item/generated’ models, the models Z-fight despite having pixels in exactly the same position.

Steps to reproduce:

1. Download and apply the attached resource pack.

2. Get a Diamond Sword and a Golden Sword from the creative inventory, and hold them in your hands.

Expected result: Both models have no Z-fighting, as the pixels of the last-rendered model should directly override the pixels of the others.

Actual result: Both models have Z-fighting, although the Golden Sword only appears to Z-fight when in the left hand first-person view.