How units spawn at construction structures.

More like how the pathing system works when units spawn at a factory. There are 2 options; bones or coding. Coding overrides bones and is what the game devs used. Presumably because it saves a ton of time exporting models.

Airfields are the only unique factory. They have a more complex pathing system for aircraft moving to and from hangars. Included a few custom examples for download as the 2 in-game airfields are nearly identical.