I'm not sure if that was just a quote you found from someone else, or your own experience... However, that green you are referring to, in this case, is due to the quality of the film they used. While it is true that the factory glass has a green hue to it, that is not something that arises with such a light tint (50% in this case) and can be avoided at darker tints if you go with higher quality. The shop I go to fixes these tint jobs on a daily basis. In other words, the shop is lying to cover their cheap quality film.
You get what you pay for with tint. There are no exceptions.