Back to something I said and that OS25 seemed okay with, I think we need to focus on the specific rule(s) that speak about what constitutes a story. DWM and Big Finish previews/trailers should not have follow the "rule one" that we have at the moment, because it has nothing to do with it. Instead, there needs to be either a new rule or an update to "rule one" that takes "parts of stories" under its wing.
This is our main problem, in my point of view, as standalone items, these comic previews and YouTube trailers are evidently not stories. But they're not supposed to be. They are supposed to be part of a story, hence why they're called "previews" and "trailers". If we can find a way to incorporate this idea of "slices of time" into "rule one" or have an alternate "rule one" altogether ("rule 1b" maybe), then we're on the home run.