A question about the origin of prefab containers

[robinheidrich]

I don't quite understand what determines the origin of a prefab container. Shouldn't it always be 0.5?

Depending on where I place the first game object, the origin is different, and it's not really easy to change it when you can't even see the value of it (only move it via origin mode).

In the context menu of the container you can't change the origin either, the options there are just grayed out.

I didn't find anything in the docs, so I'm asking here.