It's not that Racktor is saving work by having the wings mirrored, it's that there is literally no way for them to not be mirrored. There exists a texture for only one wing in the files, which the game then applies to both wings on the model.
It is still an insane number of files to edit though. Probably why I never bothered with something like this. I tend to stick with fooling around with things that don't have to be applied to every dragon texture ever. Respect, Racktor. xD