^^I was wondering about that. It seemed like a continuity error. Even if they did explain it away, it's bad writing to include a key plot point that can only be understood if you read the supplementary material. Everything the audience needs to know to follow a story should be included in the body of the work itself.
Bad writing, good marketing; that's getting more and more common in general, and has plagued the Star Wars franchise since Episode III. Not only do you have to watch the show/movie, you get hits drove to your website (and its attending advertisements) and make more money.
No, that's not it. It's entirely possible to include supplementary material that enhances or elaborates on the main body of work itself while still structuring the main work in such a way that every vital plot point is included. The supplements are for filling in the details that aren't necessary to following the basic story. For instance, you can understand
Star Trek's original pilot "The Cage" without knowing what actually happened in their fight on Rigel VII or what Vina's life was like before the episode, but those were elaborated upon in, respectively, an issue of Marvel's
Early Voyages comic and the novel
Burning Dreams. Material that the audience might be curious about but can live without is what belongs in tie-in fiction. Material that's crucial for understanding the basic plot of the story needs to be in the story itself. That's basic competence. If these people are doing the multimedia crossover stuff in such a way that the core work itself loses coherence, then they're doing it wrong.