The relevant information on that page is merely an explanation of their own policy, not a citation of an official one.
This isn't them saying that's an official policy by Lucas to default automatically there. This is simply them observing that in all games, as of yet, the light side ending was later chosen as canon. They then go on to explain that it's not clear if that means light side options were chosen throughout the story, but that they're going to assume for their articles they were.