Board Thread:General Discussion/@comment-14061097-20160420195004/@comment-26397825-20160521001811

Well, no. Fanfiction is not as factual as canon simply because to try to claim it is has a tendency to get hit by copyright laws.

You can say your story is canon up to a certain point, but after that point it is purely fictional and not factual in the slightest. You can write it, it can exist at the same time as the canon story, but they do not co-exist. One is factual and one is not. That's all there is to it, really.