“Mirrored” textures 747-8 and 787-10

I didn’t know if it was appropriate to make a new post about this, so I hope I’m correct in attaching this reply to the already started thread:

I’m not very familiar with the repaint/multiple livery aspect of flight sim, but I do notice that in some instances, there is mirroring on some of the 747-8 liveries.

My question is, what specifically causes mirroring, and how come some livery painters have mirrored images, while others don’t?
Is it caused by the re-painters, or is it caused by the team that released the original plane itself?